Question

What are the prime numbers between 20 and 70

Answer 1

23, 29, 31, 37, 41, 43, 47. 53, 59, 61, 67.

Explanation:

A prime number has no factors except 1 and itself.

Note the occurrence of 'pairs' of prime numbers eg. 29, 31 and 41, 43, which is quite common.