# The number 23

I have used this clip for many years, especially if exam dates would add up to 23. Can't believe having not included it in the math in movie collection. This is posted now on March 23, 22 and used in Lecture 23 of Math 22.
Numerologists can be obsessed with numbers. The number 23 is probably the one one is most fascinated with. One calls it the 23 Enigma. 2 and 3 are the smallest primes. 23 is the smallest prime contains successive digits. It is the smallest prime where all digits are prime. It is a factorial prime, a prime number of the form n!-1. The largest known factorial prime is 422429!+1. The birthday paradox assures that in a class of 23 or more students, there will be more than 1/2 chance that two have the same birthday. Normal human sex cells have 23 chromosomes. There are religious connections: (BC = 23 is an abbreviation for Before Christ. The Torah has 23 letters (one hidden), the Quran was revealed to the prophet in 23 years. The Mayans believed on December 23, the world would end.) In Sun Tzu's example for the Chinese remainder theorem, 23 appears as the smallest solution to x=2 (mod 3) and x=3 (mod 5) and x=2 (mod 7). Then one can play with words by translating into number. The W=23 appears as the place where the treasure is hidden in the movie It's a mad mad world.
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