I was convinced that 42 is a funny number but the last episode of “The Big Bang Theory” (4×10: The Alien Parasite Hypothesis) taught me that 73 is much more fascinating. Far from being addicted to numerology or the strange ideas of Paul Kammerer I just like number games and number theory.
Sheldon Cooper considers 73 being the best number because switching digits, 73 (21st prime number) becomes 37 (12th prime number). The number 21 includes factors 7 and 3. Seventy-three in binary (1001001) is a palindrome.
The episode aired on December 9th 2010. On December 10th the aforementioned facts were added to the Wikipedia article about 73.
Meanwhile other properties were added (as of December 12th 2010): Of the 7 binary digits representing 73, there are 3 ones. Also, 37+12=49 (seven squared) and 73+21=94=47*2, 47+2 also being equal to seven squared.
Looking behind the scences, one finds further coincidences: Sheldon’s discussion of 73 appears in the overall 73th episode of the series and Jim Parsons – the actor portraying Sheldon – was born in 1973 and, ergo, is now 37 years old (btw: Happy belated Prime Number). Jim was born on 24th of March (month No. 3) and – guess what’s 24 – 3? Right: 21! And 24 divided by 2? ok – that’s going to become a little boring …