These fields are all optional and need only be supplied if you would like a direct reply. Subject Your email address Your real name

You must answer this! If you don't, my spam filtering will ensure that I never see your email. What's 8 plus five (in digits only)?

Please make your changes here and then
Editing tips and layout rules.
File: PrimeNumber A prime number is a positive whole number that is divisible only by itself and 1. Well, almost. A prime is also divisible by the negative of itself, and -1, but we usually don't mention that. So 29 is a prime because the only numbers that divide evenly into 29 are 1, 29, -1 and -29. On the other hand, 28 is not prime because it's divisible by lots of other numbers, including 2, 4 and 7. Examples of primes are 2, 3, 5, 7, 11, 13, 17, ... In around 300BC a guy called Euclid proved that there are infinitely many primes, but there are still many things unknown about them. For example, here are some primes that differ by exactly two: * 11 and 13 * 29 and 31 * 101 and 103 Are there infinitely many such pairs? No one knows ... One of the MillenniumProblems in mathematics, namely the Riemann Hypothesis, relates to prime numbers and their distribution.