Since ancient times, mathematicians have been fascinated by problems concerning prime numbers, and many people have worked on the problem of determining ways to test if numbers are prime. One way to test if a number is prime is to find the number's divisors. The following program finds the smallest integral divisor (greater than 1) of a given number n. It does this in a straightforward way, by testing n for divisibility by successive integers starting with 2.

A coordinated project extending the list of Wieferich primes to 10^15.

Tony Forbes' extensive collection of special types of prime clusters.

This online calculator finds the Nth prime, with N up to 10^12. It also finds the pi function (given a number, this function returns the number of primes below that number).

Tables for K=300 to 999.

The formula of Jones, Sato, Wada and Wiens: the set of primes is the set of positive values taken by this expression.

A computation of the number up to 10^14, by Jörg Richstein.

Browse all prime numbers of less than 10 digits. A prime number checker facility is also included.

The top 10 k consecutive primes in arithmetic progression for each k.

Paulo Ribenboim has named this the "official" site for the collections of typos and errata from his text.