"The Big Bang Theory" The Alien Parasite Hypothesis (TV Episode 2010) - Johnny Galecki as Leonard Hofstadter

Sheldon Cooper : What is the best number? By the way, there's only one correct answer.

Raj Koothrappali : Five million, three hundred eighteen thousand and eight?

Sheldon Cooper : Wrong. The best number is 73. You're probably wondering why.

Howard Wolowitz : No.

Raj Koothrappali : We're good.

Sheldon Cooper : 73 is the 21st prime number. Its mirror, 37, is the 12th, and its mirror, 21, is the product of multiplying - hang on to your hats - seven and three. Heh? Heh? Did I lie?

Leonard Hofstadter : We get it. 73 is the Chuck Norris of numbers.

Sheldon Cooper : Chuck Norris wishes. In binary, 73 is a palindrome: 1001001, which backwards is 1001001. Exactly the same. All Chuck Norris backwards gets you is "sirron kcuhc."

Raj Koothrappali : Just for the record, when you enter 5,318,008 in a calculator, upside down, it spells "boobies."
Sheldon Cooper : Clarify something for me. Isn't the point of a communal meal the exchange of ideas and opinions? An opportunity to consider important issues of the day?

Leonard Hofstadter : It is. You just kind of put a damper on things when you said, "The next person I see talking with food in their mouth will be put to death."

Johnny Galecki: Leonard Hofstadter