100 factorial is 1*2*3*......*100
Number of multiples of 2 less than 100 = 49
Number of multiples of 3 less than 100 = 33
We are double counting those that are multiples of 2 and 3 (or 6)
Number of multiples of 6 less than 100 = 16
49+33-16 =66
There are 66 factors that are multiples or 2 or 3