23 Fascinating Maths Facts You'll Probably Never Need To Use

    Proof is left as an exercise for the reader.

    1. If you write out pi to two decimal places, backwards it spells "pie".

    2. A French word for pie chart is "camembert".

    3. The spiral shapes of sunflowers follow a Fibonacci sequence.

    4. The Fibonacci sequence is encoded in the number 1/89.

    5. A pizza that has radius "z" and height "a" has volume Pi × z × z × a.

    6. The word hundred is derived from the word "hundrath", which actually means 120 and not 100.

    7. 111,111,111 × 111,111,111 = 12,345,678,987,654,321.

    8. In a room of just 23 people there’s a 50% chance that two people have the same birthday.

    9. Zero is the only number that can't be represented in Roman numerals.

    10. (6 × 9) + (6 + 9) = 69.

    11. We tend to think of odd numbers as male and even numbers as female.

    12. If you shuffle a pack of cards properly, chances are that exact order has never been seen before in the whole history of the universe.

    13. Zero is an even number.

    14. There's not enough space in the known universe to write out a googolplex on paper.

    According to Carl Sagan in the original Cosmos series. A googolplex is 10 to the power of a googol, or 10 to the power of 10 to the power of 100. This website will write it out for you (or start... it won't ever finish because your computer won't have enough memory).

    15. The most popular favourite number is 7.

    16. That might be because 7 is "arithmetically unique".

    17. 7 also shows up a lot in human culture.

    18. The number 4 is considered unlucky in much of Asia.

    19. .999999... = 1

    20. Cicadas use prime numbers as an evolutionary strategy.

    21. 10! seconds is exactly 6 weeks.

    22. Take any four digit number, follow these steps, and you'll end up with 6174.

    23. 555 is used by some in Thailand as slang for "hahaha", because the word for "five" is pronounced "ha".

    Thanks to this Reddit thread, this Quora post and Alex Bellos' new book, Alex Through The Looking Glass for some of these facts.