How many 3 digit numbers have even no of factors?
878 three digit numbers have an even number of factors.
Every factor of a number has a pair, so there ought to be an
even number of factors for every number. However, if a pair of the
factors are the same number, then there will be an odd number of
factors, that is if the number is a perfect square.
Assuming three digit numbers are 100 to 999:
From 100 to 999, the perfect squares are 102 = 100 to 312 = 961,
a total of 31-10+1 = 22 numbers.
So of the 999-100+1 = 900 three digit numbers, 22 have an odd
number of factors, so 900-22 = 878 have an even number of