10! (read "ten factorial") is a fairly large number.

10! = 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 10 = 3628800. The decimal
expansion of ten factorial ends in two zeros.

One billion factorial (1000000000!) is much larger. Its decimal expansion
ends in a very large number of zeros.  Precisely how many zeros?

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All midshipmen submitting correct solutions to problem #105 by noon on
Friday, December 10, win a cookie. The best solution will be posted on the
problem bulletin board.
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A solution is "correct" if if it gives the correct number and explains why
that number is correct. A solution is "best" if it includes the clearest
correct explanation. Submit solutions to Prof. Hanna at mathprob@usna.edu,
or via the mailbox in Chauvenet 301.


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Problem #104 (autobiographical numbers) was quite popular. 17 midshipmen
earned cookies. Several non-midshipmen also submitted solutions. The only
seven autobiographical numbers are 1210, 2020, 21200, 3211000, 42101000,
521001000, and 6210001000.