# What is 81 factorial ?

Steps to calculate factorial of 81

## How to calculate the factorial of 81

To find 81 factorial, or 81!, simply use the formula that multiplies the number 81 by all positive whole numbers less than it.

Let's look at how to calculate the Factorial of Eighty-one :

81! is exactly : 5797126020747367985879734231578109105412357244731625958745865049716390179693892056256184534249745940480000000000000000000

Factorial of 81 can be calculated as:
81! = 81 x 80 x 79 x 78 x ... x 3 x 2 x 1

The number of trailing zeros in 81! is 19

The number of digits in 81 factorial is 121.

## What Is Factorial?

A factorial is symbolized by an integer and an exclamation symbol. In arithmetic, factorial is a multiplication function of natural numbers .

It multiplies the number by every organic number that is less than it .

Symbolically, it is listed as "!".

The function is used, among other things, to find the "n" way elements can be positioned .

## Factorial Formula

To find the factorial of any given number, exchange the exact value for n in the given equation :

n! = n × (n-1) × (n-2) × (n-3) × ….× 3 × 2 × 1

The expansion of the formula shows the numbers to be replicated together with each other to get the factorial of the number.

We can also figure out a factorial from the prior one. The factorial of any number is that number multiplied the factorial of (that number minus 1).

So the rule is : n! = n × (n−1)!

Example :
81! Factorial = 81 x 80 x 79 x 78 x ... x 3 x 2 x 1 = 81 × 80! = 5797126020747367985879734231578109105412357244731625958745865049716390179693892056256184534249745940480000000000000000000

## What are Factorials Used For?

The best use of factorial is in Combinations and Permutations.

Example : Determine how to arrange letters without repeating?

There one way for 1 letter "a":
2 ways for two letters "ab": ab, ba.
There are 6 ways for 3 letters "abc": abc acb cab bac bca.
There are 24 ways for 1234 of the letters "abcd"

## Frequently Asked Questions on Factorial

### Can we have factorials for negative numbers ?

Negative integer factorials are undefined

### What Is 0!

Zero factorial or Factorial of 0 is simple, and its own value is corresponding to 1. So, 0! = 1.