Write down separately the prime and composite numbers less than 20

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

Prime numbers less than 20 are 2, 3, 5, 7, 11, 13, 17 and 19.
Composite numbers less than 20 are 4, 6, 8, 9, 10, 12, 14, 15, 16 and 18.