Question

How many two digit integers have exactly five positive divisors?

Answer 1

Step-by-step explanation:

Since 5 is a prime number, it cannot be the product of two integers greater than 1, which implies that a number having 5 factors must be of a form of (prime)^4 --> the number of factors = (4 + 1). There are only 2 two-digit numbers which can be written this way: 2^4 = 16 and 3^4 = 81