WOLFRAM|DEMONSTRATIONS PROJECT

Factorial

​
number
100
single
double
100! =
93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000
The factorial of 4, which is written as
4!
, is
1×2×3×4=24
. Similarly,
n!=1×2×3×4×...×n
. The number
n!
grows very quickly as
n
increases. The double factorial of a number
n
, which is written as
n!!
, is an extension to the normal factorial. When
n
is odd,
n!!=n×(n-2)×(n-4)×...×5×3×1
. When
n
is even,
n!!=n×(n-2)×(n-4)×...×6×4×2
.