I don't think of a number between 1 and 20 that has exactly 5 factors what number is he thinking of

well it has to be a perfect square so that it will have 5 factors

4, 9, & 16 are the only perfect squares that are between 1 and 20 so then you just have to see which has 5 factors!

4 has the factors 1, 2, and 4 (only 3 factors)

9 has the factors 1, 3, and 9 (only 3 factors)

16 has the factors 1, 2, 4, 8, and 16 (It has 5 factors, so this is your answer)

Exactly 16 and the factors are 1 2 4 8 16