The Prime Number Spiral (a.k.a. the Ulam Spiral) is constructed as follows: Consider a rectangular grid. We start with the central point and arrange the positive integers in a spiral fashion (anticlockwise). Prime Number Spiral is a prime number spiral that shows you how square and triangular numbers are located on the spiral. The prime numbers are then marked. There is a tendency for the prime numbers to occur on diagonal lines, however far out into the spiral one goes. This is software is for exploring the Prime Number Spiral.