Any large factorial will have a number of zero behind it, and one could write an expression to compute the number of trailing zeros, but how would one go about computing the nonzero end digits?
E.g. compute first 5 nonzero end digits of (10^12)!
Any large factorial will have a number of zero behind it, and one could write an expression to compute the number of trailing zeros, but how would one go about computing the nonzero end digits? E.g. compute first 5 nonzero end digits of (10^12)! 


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This will be the least complete answer I've ever posted, but perhaps somebody else will be able to add to it. Not a complete answer (because I don't find any paper online), but I've heard JeanMarc Deshouillers speak on his (with others, but I don't recall with whom) proof that the last nonzero base$p$ digit of $n!$ forms a $q$automatic sequence. I don't recall the hypothesis on $p$, nor the connection between $p$ and $q$. But this answers (to a very limited extent) the real mathresearch level question hidden in this homework question. Or at least it would, if I could recall any details! 

