Write down separately the prime and composite numbers less than 20.

• A prime number is a number that has exactly two factors, i.e. ‘1’ and the number itself.
• A composite number has more than two factors, which means apart from getting divided by number 1 and itself,

Prime numbers less than 20 are 2, 3, 5, 7, 11, 13, 17, 19

Composite numbers less than 20 are: 4, 6, 8, 9, 10, 12, 14, 15, 16, 18