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jmc

prealgebra senior

Problem

How many positive integers less than 60 have an even number of positive divisors?
Solution
Perfect squares have an odd number of positive divisors, while all other integers have an even number of positive divisors.

The perfect squares less than or equal to 60 are 1, 4, 9, 16, 25, 36, and 49. Therefore, of the 59 positive integers less than 60, 7 of them have an odd number of factors, so of them have an even number of factors.
Final answer
52