Strong Number Or Not

July 11, 2019

Strong Number or Not:-

A strong number is a special number whose sum of the factorial of the digits is equal to the original number. For instance, the number 145 is a strong number because 1! + 4! + 5! = 145.

The following algorithm and program will help to determine if a given number is a factorial.

Algorithm to test whether a number is Strong or not:

Step 1. Start

Step 2. Ask a number from the user to test if it is a strong number.

Step 3. Store this number in a variable, say num and copy its value to a temporary variable for further calculations (originalNum =num).

Step 4. Initialize a variable to store the sum of the factorial of the digits, say sum = 0.

Step 5. Calculate the last digit of the given number and store the result in a variable. Let this variable be lastDigit = num %10.

Step 6. Calculate the factorial of the last digit and store its value in a variable, say fact.

Step 7. Add the values, in fact, to sum or, sum = sum + fact.

Step 8. Remove the last digit from num as it is not required in the later stages.

Step 9. Repeat steps 3 to 6 until the value of num is greater than zero.

Step 10. At the end of the loop, check the condition for the strong number. If sum == originalNum, then the number inserted by the user is a Strong Number, otherwise, it is not.

C Program to check wheatear a number is Strong 

/**C program to check Strong Number */
#include <stdio.h>
int main()
{
    int i, original_N, number, l_Digit, sum;
    long factorial;
    /* Ask a number from the user */
    printf("Insert a number: ");
    scanf("%d", &number);
    /* Copy the value of number to a temporary variable */
    Original_N = number;
    sum = 0;
    /* Calculate the sum of factorial of digits */
    while(number > 0)
    {
        /* Calculate the last digit of number */
        l_Digit = number % 10;
        /* Calculate the factorial of last digit */
        factorial = 1;
        for(i=1; i<=l_Digit; i++)
        {
            factorial = factorial * i;
        }
        /* Add value of factorial to sum */
        sum = sum + factorial;
        number = number / 10;
    }
    /* Condition to check Strong Number */
    if(sum == original_N)
    {
        printf("%d is STRONG NUMBER", original_N);
    }
    else
    {
        printf("%d is NOT STRONG NUMBER", original_N);
    }
    return 0;
}

Output

Insert a number: 154
145 is a STRONG NUMBER.