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

.