 Factorial

 
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 nonintegers to the nearest whole number). Factorials produce huge numbers for relatively small inputs  70! is already larger than 10^100. Zero factorial is 1.  