A factor is a number that divides into another number without a remainder. So the factors of 15 are 1, 3, 5 and 15.

The multiples of 4 are all the numbers in the 4 times table. 4,8,12,16,20,24,28,32……..

A prime number is special because it only has 2 factors. These two factors are always 1 and the number itself. So 7 is a prime number because the factors of 7 are 1 and 7.