## 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**.

## Factorials of Numbers similar to **90**

## What Is Factorial?

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

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

Symbolically, it is represented as "!".

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

## Factorial Formula

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

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

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

We can also calculate a factorial from the previous 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 integer 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.