# Tagged Questions

Questions on the factorial function, $n!=n\times(n-1)\times\cdots\times1$. Consider using the tag (gamma-function) if dealing with noninteger arguments.

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### year 10 factorial question

I would like to know the number of zeros occuring in the factorial of 2016? (2016!) I have read some ways but i don't understand it.
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### Prove $0! = 1$ from first principles

How can I prove from first principles that $0!$ is equal to $1$?
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### Finding every triplet $(n,a,b)$ such that $n!=2^a-2^b$

Question : Let $n,a,b$ be positive integers. Are there infinitely many triplets $(n,a,b)$ which satisfy the following equality?$$n!=2^a-2^b$$ If Yes, then how can we prove that? If No, then how can ...
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### Can 720! be written as the difference of two positive integer powers of 3?

Does the equation: $$3^x-3^y=720!$$ have any positive integer solution?
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### Prove that $\log(n!)\leq(\log(n))!$

Prove that $\log(n!)\leq(\log(n))!$ My attempt: I read somewhere that $n\leq\log(n!)\leq(\log(n))!$. But when I used calculator $\log(n!)$ can not be less than or equal to $(\log(n))!$. ...
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### Function order of Logarithms

How can I use Stirling's approximation to trying to find the function order of $ceil(log(logx))!$ ? My main goal is to finding it's order of complexity but my main issue is that I'm not sure on how to ...
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### Is there a way to evaluate the derivative of $x$! without using Gamma function?

Taking the factorial function $x!$ I wonder if there is a method to find the first derivative of this function without making any use of the Gamma function (or related integral representations of the ...