prime number

This is the term for a whole number (except 1) which has exactly two factors – the number itself and 1.

For example:

2 can be divided equally by 1 and 2 only, therefore it’s a prime number.

6 can be divided equally by 1, 2, 3 and 6, therefore it isn’t a prime number.

2, 3, 5, 7, 11 and 13 are prime numbers, but 1, 4, 6 and 8 aren’t.