Prime - GCSE Maths Definition

A prime number is a positive whole number, greater than 1, with exactly two (distinct) factors. More loosely, this can be remembered as numbers that can only be divided (exactly) by 1 and itself. Notice that the issue of whether 1 is a prime number is not needed, as the definition states they are greater than 1. 2 is the only even prime number. The prime numbers below 20 are 2, 3, 5, 7, 11, 13, 17 and 19. Remembering these will help you solve most problems but, for GCSE Mathematics, you are expected to recognise all prime numbers up to 100.

The sequence of prime numbers does not follow any pattern. At the time of writing, the largest known prime number has slightly over 41 000 000 digits and was discovered in late 2024. Prime numbers are often called the building blocks of mathematics - all other (whole) numbers can be produced by multiplying prime numbers together. Very large prime numbers are used in codes and internet security systems.