How many trailing zeros are there in the expansion of 1000 factorial?

1000 factorial is equal to (1000!)

The answer is 249.

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The number of trailing zeroes in the expansion of $n!$ is given by $\displaystyle \sum_{i=1}^{k} \left \lfloor \frac {n}{5^i} \right \rfloor$ where $k$ must be chosen such that $5^{k+1}>n$ .