# What is 40 factorial ?

Steps to calculate factorial of 40

## How to calculate the factorial of 40

To find 40 factorial, or 40!, simply use the formula that multiplies the number 40 by all positive whole numbers less than it.

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

40! is exactly : 815915283247897734345611269596115894272000000000

Factorial of 40 can be calculated as:
40! = 40 x 39 x 38 x 37 x ... x 3 x 2 x 1

The number of trailing zeros in 40! is 9

The number of digits in 40 factorial is 48.

## What Is Factorial?

A factorial is represented by an integer and an exclamation symbol. In math concepts, factorial is a multiplication operation of natural numbers .

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

Symbolically, it is listed as "!".

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

## Factorial Formula

To find the factorial of any given number, replace the value for n in the given rule :

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

The expansion of the formula provides numbers to be replicated together to obtain 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 :
40! Factorial = 40 x 39 x 38 x 37 x ... x 3 x 2 x 1 = 40 × 39! = 815915283247897734345611269596115894272000000000

## 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.