1 is not a prime number because it has exactly one factor (1). 2, 3, 5 and 7 are prime numbers. They each have two factors (1 and themselves). 4, 6, 8, 9 and 10 are not prime numbers because they ...

In this KS2 Maths article you’ll learn techniques to find out if a number is a prime number. We also have a KS2 Maths quiz and lots of examples.