Factorial

n! returns the factorial of n.

Attributes[Factorial] := {Listable, NumericFunction, Protected, ReadProtected}

Simple examples

In[1]:= Factorial[20]
Out[1]= 2432902008176640000

In[2]:= Factorial[5]
Out[2]= 120

Further examples

In[1]:= Factorial[0]
Out[1]= 1

In[2]:= Factorial[-1]
Out[2]= ComplexInfinity