A prime number is a number which can only be divided by itself or one. In effect this means that it has no factors, other than itself and one. With the exception of the number two, prime numbers belong to the set of natural odd numbers.

It may seem like prime numbers are random and not related to the sequence of factors which accompany the other set of composite numbers. However, if we put all the numbers in a grid and highlight the factors, we see a pattern emerging. Prime numbers appear in the gaps left behind in the sequence of factors. The pattern of factors becomes confused by the layer upon layer of subsequent factors but there is still a pattern at each stage. In a way, prime numbers are the chaotic element in the set of factors. As the numbers increase in value, the more factors there are and the less opportunity for prime numbers to emerge.