Name a pair of factors that are both prime numbers and have a product of 21

First you need to make a list of prime numbers that can only be divisible by 1 and itself.

here are examples of prime numbers: 1, 3, 5, 7, 9++

once you have a list of the prime numbers just pick all of them that add up to 21.

for example : a number divisible by only itself and one + another number divisible only by itself and one = 21