Question

The number 6 has four divisors- namely, 1,2,3, and 6. List all

numbers less than 20 that have exactly four divisors.

Answer 1

Divisors of 8: 1, 2, 4, 8

Divisors of 10: 1, 2, 5, 10

Divisors of 14: 1, 2, 7, 14

Divisors of 15: 1, 3, 5, 15