What makes 73 the Chuck Norris of numbers?
Sheldon Cooper's favourite number, the conjecture named after him, and the 2019 proof that 73 really is the only prime with its peculiar set of properties.
Varchas KoushikFounder · Storyteller & Learning Experience Designer
Have you ever wondered how a simple dialogue in a TV series could lead to a mathematical breakthrough? That's exactly what happened with Sheldon Cooper's legendary monologue about the number 73 in The Big Bang Theory.
73 is the 21st prime number. Its mirror, 37, is the 12th prime number. Its mirror, 21, is the product of multiplying — hang on to your hats — 7 by 3. In binary, 73 is a palindrome: 1001001.
Here's why 73 is such a showstopper:
- It's the 21st prime number, and its mirror, 37, is the 12th.
- 7 × 3 = 21, and the mirrors 21 and 12 are linked the same way.
- In binary, 73 is a palindrome.
Fittingly, that scene was the 73rd episode of the show. This led to the birth of the Sheldon conjecture — are there any other primes with the product property that also mirror each other? — later proven true by Carl Pomerance and Chris Spicer in 2019: 73 is the only prime with these properties.
Trivia: Jim Parsons, the actor who played Sheldon, was born in 1973. Coincidence?
Well, can't argue with Sheldon, can you? 73 is indeed the best number.
First published in the All Things Classroom newsletter
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Written by
Varchas Koushik
Founder · Storyteller & Learning Experience Designer
Founder of All Things Classroom. 10,000+ hours facilitating sessions with students across age groups and geographies; writes about game-based learning, story-driven teaching and what's possible when a lesson is designed like an experience instead of a script.
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