# What is 90 factorial ?

Steps to calculate factorial of 90

## How to calculate the factorial of 90

To find 90 factorial, or 90!, simply use the formula that multiplies the number 90 by all positive whole numbers less than it.

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

90! is exactly : 1485715964481761497309522733620825737885569961284688766942216863704985393094065876545992131370884059645617234469978112000000000000000000000

Factorial of 90 can be calculated as:
90! = 90 x 89 x 88 x 87 x ... x 3 x 2 x 1

The number of trailing zeros in 90! is 21

The number of digits in 90 factorial is 139.

## What Is Factorial?

A factorial is represented by an integer and an exclamation tag. In math concepts, factorial is a multiplication operation 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 arranged .

## Factorial Formula

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

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

The expansion of the formula provides numbers to be replicated at the same time to get the factorial of the number.

We can also work 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 :
90! Factorial = 90 x 89 x 88 x 87 x ... x 3 x 2 x 1 = 90 × 89! = 1485715964481761497309522733620825737885569961284688766942216863704985393094065876545992131370884059645617234469978112000000000000000000000

## 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.