CalcTool: Factorial calculator

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Factorial

Also performs the reverse calculation.

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$Factorial diagram$

This calc multiplies together all the whole numbers up to the input number n to give the factorial of n (=n!). It can also perform the inverse function, finding the number x that produces a factorial (x!) that you enter.

Enter either a number or a factorial in the appropriate blue box, then click "calculate". Make sure you look in the right orange box for the answer. You must enter a positive integer (whole number) in order to have a meaningful answer (the calc rounds any non-integers to the nearest whole number).
Factorials produce huge numbers for relatively small inputs - 70! is already larger than 10^100. Zero factorial is 1.