# Peterson Number in C1 min read

In this tutorial, we will learn about the Peterson number and check if the number is Peterson or not in C.

## What is Peterson Number?

A number is said to be a Peterson number if the sum of factorials of each digit of the number is equal to the number itself.

Peterson numbers examples:

`Number = 145145 = !1 + !4 + !5= 1 + 4*3*2*1 + 5*4*3*2*1= 1 + 24 + 120= 145 = 145`

Therefore, we can see that after the sum of the factorial of 145 is equal to the number 145 itself. Hence the Peterson Number.

## C Program to check whether the number is Peterson Number or not

Peterson number program in C:

Output 1:

`Enter a number: 145 145 is a Peterson number`

Output 2:

`Enter a number: 55 55 is not a Peterson number`

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