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Write C program to find a Strong number

When the sum of the factorial of each individual digit is equal to an original number then a number is said to be a strong number. For example 145=1! + 4! + 5! are Strong numbers.

List of Strong number are: 1, 2, 145, 40585, ..

C program to check strong number

In this program, you will write a C program to check whether the number entered by the user is a Strong number or not.


#include <stdio.h>
int main()
{
    int remainders,fact,sum=0,i,num,copynum;
    printf("Enter the number:");
    scanf("%d",&num);
    copynum=num;
    while(num!=0)
    {
        remainders=num%10;
        fact=1;
        for(i=1;i<=remainders;i++)
        {
            fact=fact*i;
        }
        sum=sum+fact;
        num=num/10;
    }
    if(sum==copynum)
    {
        printf("%d is strong numbers",copynum);
    }
    else
    {
        printf("%d is not a strong numbers",copynum);
    }
    return 0;
}

output

Enter the number:145
145 is strong numbers

Check Strong Number explanation

In this program, you will take a number from the user and store it in variable num.
copy the value of num into another variable copynum for verification purposes i.e copynum=num.
Inside the loop find the last digit of the given number num and stored the last digit value in remainders variables i.e remainder=num%10.
find the factorial of remainders value and store it in variable fact.
```
for(i=1;i<=remainders;i++)
 { 
        fact=fact*i;
 }
```
add the factorial value in the variable sum. sum=sum+fact
divide num by 10. so that it removes the last digit from the num variable as it is not needed anymore. num=num/10
you will repeat steps 3 to 6 until num is 0.
after the end, you will check whether copynum is the same as the sum value i.e sum==copynum. if it is the same, then the number is strong otherwise it is not a strong number.

Program to find strong number from 1 to n


#include <stdio.h>
int main() 
{
    int remainders,sum,fact,range,i,num,n;
    printf("\n Enter the range:");
    scanf("%d",&range);
    printf("\n strong number from 1 to n are:");
    for(n=1;n<=range;n++)
    {
	sum=0;
        num=n;
        while(num>0)
        {
            remainders=num%10;
            fact=1;
            for(i=1;i<=remainders;i++)
            {
                fact=fact*i;
            }
            sum=sum+fact;
            num=num/10;
        }
        if(sum==n)
        {
            printf("\t%d",n);
        }
    }
    return 0;
}

output

Program to find strong number in a given range

#include <stdio.h>
int main() 
{
    int remainders,sum,fact,lower,upper,i,num,n;
    printf("Enter the lower range:");
    scanf("%d",&lower);
    printf("Enter the upper range:");
    scanf("%d",&upper);
    printf("strong number from %d to %d are:",lower,upper);
    for(n=lower;n<=upper;n++)
    {
        sum=0;
        num=n;
        while(num>0)
        {
            remainders=num%10;
            fact=1;
            for(i=1;i<=remainders;i++)
            {
                fact=fact*i;
            }
            sum=sum+fact;
            num=num/10;
        }
        if(sum==n)
        {
            printf("\t%d",n);
        }
    }
    return 0;
}

output

Enter the lower range:2
Enter the upper range:400
strong number from 2 to 400 are: 2       145

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