Prime+Numbers

Sieve of Eratosthenes [| Prime Number Trick] Using prime numbers, you can amaze your friends with a prime prediction... Without knowing which prime number your friends picked, you can still tell them:
 * Ask your friends to pick any prime number bigger than 5, but they must not tell you what it is.
 * Square it. (In other words multiply the prime number by itself.)
 * Add 17
 * Divide by 12


 * //There will be a remainder of 6.// **

(Or if they do the sum on a calculator, the answer will end with " .5")