Prime numbers up to 100 KS2 Revision

Things to remember:

• You need to know the prime numbers between 1 and 20
• 1 isn’t a prime number
• 2 is the only even prime number

A prime number is a positive whole number bigger than 1 that only has two factors, itself and 1.

For example, 13 is a prime number because its only factors are 1 and 13.

You need to learn the prime numbers between 1 and 20:

2 3 5 7

11 13 17 19

2 is a special prime, because it is the only even prime. All other even numbers can be divided by 2, so can’t be prime.

You need to be able to tell if a number smaller than 100 is prime.

Is 59 a prime number?

If you can’t divide a number less than 100 by 2, 3,5, or 7 and get a whole number, then it is prime.

59\div2=29.5

59 \div 3 = 19.6666...

59 \div 5 = 11.8

59 \div 7 = 8.42…

59 is a prime number!