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# Program to check for Peterson number

• Difficulty Level : Expert
• Last Updated : 09 Apr, 2021

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.

Example:

```Input : n = 145
Output = Yes
Explanation:
145 = 5! + 4! + 1!
= 120 + 24 +1
= 145

Input  : n = 55
Output : No
Explanation: 5! + 5!
= 120 + 120
= 240
Since 55 is not equal to 240
It is not a Peterson number.     ```

We will pick each digit (Starting from the last digit) of the given number and find its factorial. And add all factorials. Finally, we check if the sum of factorials is equal to number or not.

## C++

 `// C++ program to determine whether the number is``// Peterson number or not``#include ``using` `namespace` `std;` `// To quickly find factorial of digits``int` `fact[10]``    ``= { 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880 };` `// Function to check if a number is Peterson``// or not``bool` `peterson(``int` `n)``{``    ``int` `num = n, sum = 0;` `    ``// stores the sum of factorials of``    ``// each digit of the number.``    ``while` `(n > 0) {``        ``int` `digit = n % 10;``        ``sum += fact[digit];``        ``n = n / 10;``    ``}` `    ``// Condition check for a number to``    ``// be a Peterson Number``    ``return` `(sum == num);``}` `// Driver Program``int` `main()``{``    ``int` `n = 145;``    ``if` `(peterson(n))``        ``cout << ``"Yes"``;``    ``else``        ``cout << ``"No"``;``    ``return` `0;``}`

## Java

 `// java program to determine whether the``// number is Peterson number or not``import` `java.io.*;` `public` `class` `GFG {` `    ``// To quickly find factorial of digits``    ``static` `int``[] fact``        ``= ``new` `int``[] { ``1``,   ``1``,   ``2``,    ``6``,     ``24``,``                      ``120``, ``720``, ``5040``, ``40320``, ``362880` `};` `    ``// Function to check if a number is``    ``// Peterson or not``    ``static` `boolean` `peterson(``int` `n)``    ``{``        ``int` `num = n;``        ``int` `sum = ``0``;` `        ``// stores the sum of factorials of``        ``// each digit of the number.``        ``while` `(n > ``0``) {``            ``int` `digit = n % ``10``;``            ``sum += fact[digit];``            ``n = n / ``10``;``        ``}` `        ``// Condition check for a number to``        ``// be a Peterson Number``        ``return` `(sum == num);``    ``}` `    ``// Driver Program``    ``static` `public` `void` `main(String[] args)``    ``{``        ``int` `n = ``145``;` `        ``if` `(peterson(n))``            ``System.out.println(``"Yes"``);``        ``else``            ``System.out.println(``"No"``);``    ``}``}` `// This code is contributed by vt_m.`

## Python3

 `# Python3 code to determine whether the``# number is Peterson number or not` `# To quickly find factorial of digits``fact ``=` `[``1``, ``1``, ``2``, ``6``, ``24``, ``120``, ``720``,``        ``5040``, ``40320``, ``362880``]` `# Function to check if a number``# is Peterson or not`  `def` `peterson(n):``    ``num ``=` `n``    ``sum` `=` `0` `    ``# stores the sum of factorials of``    ``# each digit of the number.``    ``while` `n > ``0``:``        ``digit ``=` `int``(n ``%` `10``)``        ``sum` `+``=` `fact[digit]``        ``n ``=` `int``(n ``/` `10``)` `    ``# Condition check for a number``    ``# to be a Peterson Number``    ``return` `(``sum` `=``=` `num)`  `# Driver Code``n ``=` `145``print``(``"Yes"` `if` `peterson(n) ``else` `"No"``)` `# This code is contributed by "Sharad_Bhardwaj"..`

## C#

 `// C# program to determine whether the``// number is Peterson number or not``using` `System;` `public` `class` `GFG {` `    ``// To quickly find factorial of digits``    ``static` `int``[] fact``        ``= ``new` `int``[10] { 1,   1,   2,    6,     24,``                        ``120, 720, 5040, 40320, 362880 };` `    ``// Function to check if a number is``    ``// Peterson or not``    ``static` `bool` `peterson(``int` `n)``    ``{``        ``int` `num = n;``        ``int` `sum = 0;` `        ``// stores the sum of factorials of``        ``// each digit of the number.``        ``while` `(n > 0) {``            ``int` `digit = n % 10;``            ``sum += fact[digit];``            ``n = n / 10;``        ``}` `        ``// Condition check for a number to``        ``// be a Peterson Number``        ``return` `(sum == num);``    ``}` `    ``// Driver Program``    ``static` `public` `void` `Main()``    ``{``        ``int` `n = 145;` `        ``if` `(peterson(n))``            ``Console.WriteLine(``"Yes"``);``        ``else``            ``Console.WriteLine(``"No"``);``    ``}``}` `// This code is contributed by vt_m.`

## PHP

 ` 0)``    ``{``        ``\$digit` `= ``\$n` `% 10;``        ``\$n` `= ``\$n` `/ 10;    ``    ``}` `    ``// Condition check for``    ``// a number to be a``    ``// Peterson Number``    ``return` `(``\$sum` `== ``\$num``);``}` `    ``// Driver Code``    ``\$n` `= 145;``    ``if` `(peterson(``\$n``))``        ``echo` `"Yes"``;``    ``else``        ``echo``"No"``;``    ` `// This code is contributed by ajit``?>`

## Javascript

 ``

Output:

`Yes`

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