Prime numbers are special numbers that can only be divided by themselves and 1. 19 is a prime number. It can only be divided by 1 and 19. 9 is not a prime number. It can be divided by 3 as well as ...

Remember, a prime numbers can only be divided by itself and 1. You can use your knowledge of multiples (times tables) to eliminate numbers. Start with the smallest numbers and work your way up.