If x = a!, which of these following values of a is the least possible value (in this list) for which the last 6 digits of the integer x will all be zero? Choices:
A) 18  B) 24  C) 29  D) 34  E) 38
2*5 will give one 0 at the end. We need 2^6*5^6 to get 6 zeroes at the end.   There are many 2's, so we need to find the first 6 appearances of 5.   These multiples of 5 are: 5, 10, 15, 20, 5*5...which gives us 6.   To have at least 6 zeroes at the end, a =&gt; 25.   The answer is 29.
<result>C</result>
If x = a!, which of these following values of a is the least possible value (in this list) for which the last 6 digits of the integer x will all be zero?