The Big Bang Theory': The Real Reason Behind All Of Sheldon's '73' T-Shirts

Fans of The Big Bang Theory have come to love Sheldon Cooper and all his quirks. However, there remains one thing about the character that still has audiences confused.

What's the deal with Sheldon and the number 73?

The character has referred to 73 as the Chuck Norris of numbers, and he often wears t-shirts with the number on it.

According to Radio Times, there are plenty of reasons for Sheldon's obsession. Chief among them - actor Jim Parsons was born in the year 1973. If you know Sheldon Cooper though, you know that the man would never have a favorite anything without a mathematical or scientific reason.

This is where that Chuck Norris comment comes in. According to Sheldon, the number 73 has a lot of coincidences attached to it. In the episode titled "The Alien Parasite Hypothesis" (which is actually episode number 73), Sheldon explains why it's so special.

More TV: The Exorcist Season 2 Gets Premiere Date

"73 is the 21st prime number," Sheldon explains. "Its mirror, 37, is the 12th and its mirror, 21, is the product of multiplying 7 and 3 ... and in binary 73 is a palindrome, 1001001, which backwards is 1001001."

So, long story short, 73 is an incredibly unique number that also happens to fit the actor himself. It's a wild situation, to be sure.

Up Next: Fox Unveils Fall TV Premiere Schedule