What is the greatest integer m for which the number 20!/10^m is an integer?  Choose the correct choice from the following answers
A) 3 B) 4 C) 5 D) 6 E) 7
10^m = 2^m*5^m.   Let's figure out how many 5's are in the prime factorization of 20!   The multiples of 5 are: 5, 10, 15, 20.   Thus 5^4 will divide 20! but 5^5 will not.   Clearly 2^4 will divide 20!   So m=4 is the largest possible integer.   The answer is 4.
<result>B</result>
What is the greatest integer m for which the number 20!/10^m is an integer?