### 23 things you always wanted to know about numbers

(stolen shamelessly from the observer

1 If your precocious nine-year old daughter asked you to place one penny on the first square of a chessboard, two pence on the second square, four pence on the third, and so on, you would need to put £92 million billion on the 64th and final square.

2 Prime numbers (2, 3, 5, 7, 13 and so on ...) are divisible only by themselves and the number one. The largest prime number yet discovered has 2,098,960 digits. If we were to print nothing except this number across all sections of today's and next week's Observers (containing around 250,000 words in each issue) we could just about fit the number in.

3 'Three is the magic number', according to 'Daisy Age' hip-hop pioneers De la Soul. Dante Alighieri clearly agreed. The Divine Comedy, written from 1306-21, is based on multiples of three - three books of 33 cantos of three-line stanzas, representing the Holy Trinity.

4 If you bought a ticket today for next Saturday's National Lottery there would be less chance of you winning (13.9 million to one) than of your being dead by the time of the draw. As many as 20,000 Britons choose the numbers 1, 2, 3, 4, 5 and 6 in an average week - meaning they would each scoop a miserly £10,000 or less on a jackpot win. You have the greatest chance of not sharing your jackpot if you pick the least popular numbers - 36, 41, 46, 47, 48, 49.

5 The 99 Flake: According to Italian legend, there was a king who had an elite guard of 99 men known as 'the 99'. These were the best troops in the land, so 99 came to mean 'the best there is'. Cadbury hoped that naming the short Flake for ice creams after the elite guard would give their product some of the guards' aura of greatness and make it appeal to the Italian ex-pats who dominated the British ice cream trade at the time.

6 Six key numbers, thought to have special significance in the 'Big Bang' theory of the creation of the universe, determine the essential features of the world in which we ive. If one were to alter any of these numbers by the smallest fraction, then a universe that could sustain stars, galaxies and conscious life would then become impossible. The best concise explanation of these recent discoveries can be found in Astronomer Royal Sir Martin Rees's book Just Six Numbers.

7 At sixes and sevens: The seven major London trading associations, known as livery companies, were ranked from number one to seven in order of precedence in the sixteenth century. The Merchant Taylors and the Skinners vied with each other to get off the bottom of the table and swapped places frequently. Hence, they were at sixes and sevens but could rarely get their act together enough to go higher.

8 You would need just four colours to fill in the map of the world so that no two neighbouring countries ever have the same colour. And no matter how you redraw the borders, four colours will always be enough.

9 What have the Arabs ever done for us? Nothing, or zero to be more precise. Abstract mathematics were a mystery to the Western world until the introduction of the number zero from Arabia in the tenth century. The concept was first proposed by the mathematician and astronomer Muhammad Bin Ahmad in 967 AD. Numbers had, until that point, been used to count, not to reason, and the idea of having zero goats, for example, was a nonsense - you either had something, or you didn't. But while, as a result, we call our system of numbers Arabic numbers, in the Arab world the numerals are called Indian numbers because they originated further east still.

10 The number of pairs of rabbits that would have been spawned 100 months after the first pair of rabbits bred, if each pair bred every month, would be 3.5 billion billion, according to the example given by the thirteenth Century Italian mathematician Fibonacci in his seminal work Liber Abaci , the book which brought modern mathematics to scholarly prominence in the west.

11 The average adult in Britain has a vocabulary of 50,000 words. However, as there are 290,000 words in the Oxford English Dictionary, and well over half a million once you count plurals and variations on words, this is almost pathetically inarticulate.

12 There is currently £32.6 billion cash in notes and coins in circulation in Britain. This equates to about £540 for every person in Britain. However, of this, there is estimated to be at least £50 million languishing down the backs of the nation's sofas and under car seats.

13 Fear of the number 13 (or Triskaidekaphobia) has struck many people including Franklin Delano Roosevelt, who was terrified of dining at a table of 13. Paraskevidekatriaphobics have a morbid fear of Friday the 13th, which falls at least once a year and sometimes three times, and will be dreading 2009, the next triple whammy year. Charles Manson, Jeffrey Dahmer, Frederick West and Jack the Ripper all contain 13 letters in their names. Spookily, eleven plus two is an anagram of twelve plus one.

14 However, Italians love the number 13, but believe 17 is inauspicious. In Japan, the number four is unlucky because the Japanese word for four, shi, sounds like the word for death.

15 3.141... Much of physics depends on the number of Pi, celebrated on 14 March (3/14) by American maths fans. It measures the ratio between a circle's circumference and its diameter and is a number which continues without end. Lancashire taxi driver Tom Morton's attempt to break the British record by reciting Pi's first 20,014 numbers, in sequence, failed after 15,220 digits due to a typo on his revision notes. Japanese researchers have calculated Pi to 1.2411 trillion places. Late at night, mathematical philosophers like to ponder 'What shape would a circle be if Pi were exactly 3?'

16 Another number without end is the Golden Mean, which is the ratio of 1.618.../1, much loved by mathematicians who believe the natural world contains a symmetrical beauty. This ratio is replicated in everything from the shape of the Parthenon in Athens, to picture frames to credit cards. Bizarrely, measuring from the tip, each of the three bones in the human finger is 1.618 times longer than the one before it.

17 The world's worst ever statistical prediction was that by IBM chief Thomas Watson who said in 1943 that there would only ever be enough demand for five computers in the world. There were more than 100 million by the turn of the millennium.

18 Eleven days were skipped in 1752 when the Gregorian calendar replaced the previous Julian calendar, which had got out of synch due to inaccuracies in measuring the earth's orbit. A London mob rioted, furious at losing eleven days of their lives.

19 The chances of anybody being struck by lightning are less than one in 1,000,000. Kevin Parent of Pennsylvania might be best off staying indoors on wet days, however, after being hit from on high three times in five years, which gives him a strong claim to be the world's unluckiest man.

20 Thomas Burke won the men's 100 metres at the first modern Olympics in Athens 1896. With his winning time of 12 seconds, he would only just have passed the 80m mark when Maurice Greene was crossing the finishing line in Sydney 2000 in 9.87secs. Greene ran at an average of 24.23 miles per hour, while Burke trundled along at 20mph.

21 For both Christianity and Islam, the numbers 12 and 40 are deeply significant. Jesus spent 40 days and 40 nights in the desert and Moses spent 40 days on the mountain waiting for the Ten Commandments. The Shia wait 40-days after a martyr's death before beginning the period of lamentation. Jesus had 12 apostles (excluding the unlucky thirteenth, Judas Iscariot), while there are 12 Imams according to the largest Shia group. The last in the line went into hiding in AD941 and his followers are still waiting for his reappearance.

22 Attempts to renew the popular appeal of bingo have seen a recent modernisation of the bingo callers' lingo. 71 is no longer 'bang on the drum' but 'J-Lo's bum'. Old favourites such as 'two fat ladies', 88, 'clickety click', 66, and 'legs eleven' are staying put, but 'Danny la Rue', 52, has made way for the shoe designer 'Jimmy Choo'.

23 Infinity is the largest number of all. Except, of course, for infinity plus one.

1 If your precocious nine-year old daughter asked you to place one penny on the first square of a chessboard, two pence on the second square, four pence on the third, and so on, you would need to put £92 million billion on the 64th and final square.

2 Prime numbers (2, 3, 5, 7, 13 and so on ...) are divisible only by themselves and the number one. The largest prime number yet discovered has 2,098,960 digits. If we were to print nothing except this number across all sections of today's and next week's Observers (containing around 250,000 words in each issue) we could just about fit the number in.

3 'Three is the magic number', according to 'Daisy Age' hip-hop pioneers De la Soul. Dante Alighieri clearly agreed. The Divine Comedy, written from 1306-21, is based on multiples of three - three books of 33 cantos of three-line stanzas, representing the Holy Trinity.

4 If you bought a ticket today for next Saturday's National Lottery there would be less chance of you winning (13.9 million to one) than of your being dead by the time of the draw. As many as 20,000 Britons choose the numbers 1, 2, 3, 4, 5 and 6 in an average week - meaning they would each scoop a miserly £10,000 or less on a jackpot win. You have the greatest chance of not sharing your jackpot if you pick the least popular numbers - 36, 41, 46, 47, 48, 49.

5 The 99 Flake: According to Italian legend, there was a king who had an elite guard of 99 men known as 'the 99'. These were the best troops in the land, so 99 came to mean 'the best there is'. Cadbury hoped that naming the short Flake for ice creams after the elite guard would give their product some of the guards' aura of greatness and make it appeal to the Italian ex-pats who dominated the British ice cream trade at the time.

6 Six key numbers, thought to have special significance in the 'Big Bang' theory of the creation of the universe, determine the essential features of the world in which we ive. If one were to alter any of these numbers by the smallest fraction, then a universe that could sustain stars, galaxies and conscious life would then become impossible. The best concise explanation of these recent discoveries can be found in Astronomer Royal Sir Martin Rees's book Just Six Numbers.

7 At sixes and sevens: The seven major London trading associations, known as livery companies, were ranked from number one to seven in order of precedence in the sixteenth century. The Merchant Taylors and the Skinners vied with each other to get off the bottom of the table and swapped places frequently. Hence, they were at sixes and sevens but could rarely get their act together enough to go higher.

8 You would need just four colours to fill in the map of the world so that no two neighbouring countries ever have the same colour. And no matter how you redraw the borders, four colours will always be enough.

9 What have the Arabs ever done for us? Nothing, or zero to be more precise. Abstract mathematics were a mystery to the Western world until the introduction of the number zero from Arabia in the tenth century. The concept was first proposed by the mathematician and astronomer Muhammad Bin Ahmad in 967 AD. Numbers had, until that point, been used to count, not to reason, and the idea of having zero goats, for example, was a nonsense - you either had something, or you didn't. But while, as a result, we call our system of numbers Arabic numbers, in the Arab world the numerals are called Indian numbers because they originated further east still.

10 The number of pairs of rabbits that would have been spawned 100 months after the first pair of rabbits bred, if each pair bred every month, would be 3.5 billion billion, according to the example given by the thirteenth Century Italian mathematician Fibonacci in his seminal work Liber Abaci , the book which brought modern mathematics to scholarly prominence in the west.

11 The average adult in Britain has a vocabulary of 50,000 words. However, as there are 290,000 words in the Oxford English Dictionary, and well over half a million once you count plurals and variations on words, this is almost pathetically inarticulate.

12 There is currently £32.6 billion cash in notes and coins in circulation in Britain. This equates to about £540 for every person in Britain. However, of this, there is estimated to be at least £50 million languishing down the backs of the nation's sofas and under car seats.

13 Fear of the number 13 (or Triskaidekaphobia) has struck many people including Franklin Delano Roosevelt, who was terrified of dining at a table of 13. Paraskevidekatriaphobics have a morbid fear of Friday the 13th, which falls at least once a year and sometimes three times, and will be dreading 2009, the next triple whammy year. Charles Manson, Jeffrey Dahmer, Frederick West and Jack the Ripper all contain 13 letters in their names. Spookily, eleven plus two is an anagram of twelve plus one.

14 However, Italians love the number 13, but believe 17 is inauspicious. In Japan, the number four is unlucky because the Japanese word for four, shi, sounds like the word for death.

15 3.141... Much of physics depends on the number of Pi, celebrated on 14 March (3/14) by American maths fans. It measures the ratio between a circle's circumference and its diameter and is a number which continues without end. Lancashire taxi driver Tom Morton's attempt to break the British record by reciting Pi's first 20,014 numbers, in sequence, failed after 15,220 digits due to a typo on his revision notes. Japanese researchers have calculated Pi to 1.2411 trillion places. Late at night, mathematical philosophers like to ponder 'What shape would a circle be if Pi were exactly 3?'

16 Another number without end is the Golden Mean, which is the ratio of 1.618.../1, much loved by mathematicians who believe the natural world contains a symmetrical beauty. This ratio is replicated in everything from the shape of the Parthenon in Athens, to picture frames to credit cards. Bizarrely, measuring from the tip, each of the three bones in the human finger is 1.618 times longer than the one before it.

17 The world's worst ever statistical prediction was that by IBM chief Thomas Watson who said in 1943 that there would only ever be enough demand for five computers in the world. There were more than 100 million by the turn of the millennium.

18 Eleven days were skipped in 1752 when the Gregorian calendar replaced the previous Julian calendar, which had got out of synch due to inaccuracies in measuring the earth's orbit. A London mob rioted, furious at losing eleven days of their lives.

19 The chances of anybody being struck by lightning are less than one in 1,000,000. Kevin Parent of Pennsylvania might be best off staying indoors on wet days, however, after being hit from on high three times in five years, which gives him a strong claim to be the world's unluckiest man.

20 Thomas Burke won the men's 100 metres at the first modern Olympics in Athens 1896. With his winning time of 12 seconds, he would only just have passed the 80m mark when Maurice Greene was crossing the finishing line in Sydney 2000 in 9.87secs. Greene ran at an average of 24.23 miles per hour, while Burke trundled along at 20mph.

21 For both Christianity and Islam, the numbers 12 and 40 are deeply significant. Jesus spent 40 days and 40 nights in the desert and Moses spent 40 days on the mountain waiting for the Ten Commandments. The Shia wait 40-days after a martyr's death before beginning the period of lamentation. Jesus had 12 apostles (excluding the unlucky thirteenth, Judas Iscariot), while there are 12 Imams according to the largest Shia group. The last in the line went into hiding in AD941 and his followers are still waiting for his reappearance.

22 Attempts to renew the popular appeal of bingo have seen a recent modernisation of the bingo callers' lingo. 71 is no longer 'bang on the drum' but 'J-Lo's bum'. Old favourites such as 'two fat ladies', 88, 'clickety click', 66, and 'legs eleven' are staying put, but 'Danny la Rue', 52, has made way for the shoe designer 'Jimmy Choo'.

23 Infinity is the largest number of all. Except, of course, for infinity plus one.