You're not just the average, ordinary fan of the hit television show The Big Bang Theory. You're a nerd, and you want to show it off it style! Now you can do it with this cool 73 shirt worn by Sheldon Cooper. 73 is a special number for a various different number of reasons. If you're a fan, chances are you know the significance of this awesome number, so why not show off your geeky knowledge with this officially licensed Big Bang Theory t-shirt? "The best number is 73. Why? 73 is the 21st prime number. Its mirror (37) is the 12th and its mirror (21) is the product of multiplying 7 and 3. ... In binary, 73 is a palindrome, 1001001 which backwards is 1001001." This episode is the 73rd episode in the entire Big Bang Theory series.