Write down separately the prime and composite numbers less than 20

Solution:

Prime numbers are the numbers that have only two factors, that are, 1 and the number itself. However, most numbers have more than two factors, and they are called composite numbers. 

A prime number is a number that has only two factors, 1 and the number itself.

A composite number is a number that has more than two factors.

Therefore, the prime numbers from 1 to 20 are 2, 3, 5, 7, 11, 13, 17, and 19 and the composite numbers from 1 to 20 are 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, and 20.

Write down separately the prime and composite numbers less than 20

Summary:

The prime numbers from 1 to 20 are 2, 3, 5, 7, 11, 13, 17, and 19 and the composite numbers from 1 to 20 are 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, and 20.