Number Theory
posted by Carol .
What characteristic do the numbers 8, 10, 15, 26, and 33 have that the numbers 5, 9, 16, 18, and 24 donâ€™t
have? (Hint: List the factors of the numbers.) Give two more numbers that have this characteristic.

Don't 8, 10, 15, 26, and 33 each have only 4 factors? (i.e., 1, 8, 2, 4)
The others have more or less than 4 factors.