Pythagoras' Constant is the square root of two.
You've probably heard of the Pythagorean Theorem from 10th grade geometry class, but have you heard of Pythagoras' Constant? So, here's the skinny: Pythagoras' Constant is the square root of 2 (1.41). It's also the first irrational number ever discovered.
Fun Fact! There is just one number that is spelled with the same number of letters as the number itself.