Did you know?

Did you know that if a prime number is P, and a random number is A, then (A^P-A) is divisible by P?
This equation is named Fermat's Little Theorem.

Did you also know that there is a "bigger" one named Wilson's Theorem, where [(P-1)!+1] is divisible by P?
Wilson's theorem is bigger is a sense that if P gets too big, it would be quite difficult to calculate.