Write a C program to input number from user and check whether number is Strong number or not. How to check strong numbers using loop in C programming. Logic to check strong number in C programming.

**Example**

**Input**

Input number: 145

**Output**

145 is STRONG NUMBER

## Required knowledge

Basic C programming, If else, For loop, While loop, Nested loop

### What is Strong number?

Strong number is a special number whose sum of factorial of digits is equal to the original number.

For example: 145 is strong number. Since, `1! + 4! + 5! = 145`

## Logic to check Strong number

Step by step descriptive logic to check strong number.

- Input a number from user to check for strong number. Store this in a variable say
`num`. Copy it to a temporary variable for calculations purposes, say`originalNum = num`

. - Initialize another variable to store sum of factorial of digits, say
`sum = 0`

. - Find last digit of the given number
`num`. Store the result in a variable say`lastDigit = num % 10`

. - Find factorial of
`lastDigit`. Store factorial in a variable say`fact`. - Add factorial to
`sum`i.e.`sum = sum + fact`

. - Remove last digit from
`num`as it is not needed further. - Repeat steps 3 to 6 till
`num > 0`

. - After loop check condition for strong number. If
`sum == originalNum`

, then the given number is Strong number otherwise not.

Learn more - Program to find sum of digits of number.

## Program to check Strong number

```
/**
* C program to check whether a number is Strong Number or not
*/
#include <stdio.h>
int main()
{
int i, originalNum, num, lastDigit, sum;
long fact;
/* Input a number from user */
printf("Enter any number to check Strong number: ");
scanf("%d", &num);
/* Copy the value of num to a temporary variable */
originalNum = num;
sum = 0;
/* Find sum of factorial of digits */
while(num > 0)
{
/* Get last digit of num */
lastDigit = num % 10;
/* Find factorial of last digit */
fact = 1;
for(i=1; i<=lastDigit; i++)
{
fact = fact * i;
}
/* Add factorial to sum */
sum = sum + fact;
num = num / 10;
}
/* Check Strong number condition */
if(sum == originalNum)
{
printf("%d is STRONG NUMBER", originalNum);
}
else
{
printf("%d is NOT STRONG NUMBER", originalNum);
}
return 0;
}
```

Output

Enter any number to check Strong number: 145 145 is STRONG NUMBER

Happy coding 😉

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