Find strong numbers between an interval

Posted on Apr 8, 2020

C program to find Strong Numbers within a range of numbers.

When the sum of the factorial of a number’s individual digits is equal to the number itself, then that number is called a strong number.

For example, Let num = 145
Sum of factorial of digits = 1! + 4! + 5! = 1 + 24 + 120 = 145
Hence, 145 is a strong number

Some of the strong numbers are: 1, 2, 145, 40585, ...

Program 

#include<stdio.h>
#include<conio.h>
void main()
{
	int low, high, i, j, k, fact, sum, temp;

    printf("Enter two numbers (interval)\t:");
    scanf("%d%d",&low,&high);

    printf("Strong numbers between %d and %d are\t:",low,high);
    for(k=low;k<=high;k++)
    {
        sum = 0;
        temp = k;
        while(temp > 0)
        {
            i = temp % 10;
            fact = 1;
            for(j=1;j<=i;j++)
            {
                fact = fact * j;
            }
            sum = sum + fact;
            temp = temp / 10;
        }
        if(k == sum)
            printf("%d, ",k);
    }
    getch();
}

Output 

Enter two numbers (interval)    :1
50000
Strong numbers between 1 and 50000 are  :1, 2, 145, 40585,