# What is 91 factorial ?

Steps to calculate factorial of 91

## How to calculate the factorial of 91

To find 91 factorial, or 91!, simply use the formula that multiplies the number 91 by all positive whole numbers less than it.

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

91! is exactly : 135200152767840296255166568759495142147586866476906677791741734597153670771559994765685283954750449427751168336768008192000000000000000000000

Factorial of 91 can be calculated as:
91! = 91 x 90 x 89 x 88 x ... x 3 x 2 x 1

The number of trailing zeros in 91! is 21

The number of digits in 91 factorial is 141.

## What Is Factorial?

A factorial is displayed by an integer and an exclamation tag. In math concepts, factorial is a multiplication process of natural numbers .

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

Symbolically, it is represented as "!".

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

## Factorial Formula

To find the factorial of any given number, change the exact value for n in the given method :

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

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

We can also measure a factorial from the previous one. The factorial of any number is that number replicated the factorial of (that number minus 1).

So the rule is : n! = n × (n−1)!

Example :
91! Factorial = 91 x 90 x 89 x 88 x ... x 3 x 2 x 1 = 91 × 90! = 135200152767840296255166568759495142147586866476906677791741734597153670771559994765685283954750449427751168336768008192000000000000000000000

## 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 number factorials are undefined

### What Is 0!

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