Friday, July 22, 2016

elementary number theory - Compute largest integer power of 6 that divides 73!



I am looking to compute the largest integer power of 6 that divides 73!



If it was something smaller, like 6! or even 7!, I could just use trial division on powers of 6. However, 73! has 106 decimal digits, and thus trial division isn't optimal.



Is there a smarter way to approach this problem?


Answer




HINT: There are 73/3=24 numbers divisible by 3, 73/9=8, numbers divisible by 9, 73/27=2 numbers divisible by 27 in the set [1,73]N. It should be easy now to obtain that the answer is 34 (with the value 634).


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