Question

some positive integers have exactly four positive factors. for example, 35 has only 1, 5, 7 and 35 as its factors. what is the sum of the smallest five positive integers that each have exactly four positive factors?

Answer 1

The smallest five positive integers that each have exactly four factors are 6, 8, 10, 14, and 15.

6 + 8 + 10 + 14 + 15 = 53