C Program to Find Krishnamurthy Number

Krishnamurthy Number:- It is a number that is equal to the sum of the factorial of all its digits. For example 1, 2, 145. Sometimes it is also called as a Strong number or Peterson number. In this post, we will write a program for Krishnamurthy Number in C.

Examples of Krishnamurthy Number

1! = 1
So, 1 is a Krishnamurthy number.

Similarly,
2! = 1*2 = 2
2 is also a Krishnamurthy number.

145
=> 1! + 4! + 5!
=> 1 + 24 + 120
=> 145
The sum of the factorial of individual digits is the same as the original number 145. Hence, 145 is a Krishnamurthy number.

Similarly,
40585
=> 4! + 0! + 5! + 8! + 5!
=> 24 +1 + 120 + 40320 + 120
=> 40585

Hence the numbers 1, 2, 145 and 40585 are Krishnamurthy number.

151
=> 1! + 5! + 1!
=> 1 + 120 + 1
=> 122
The sum of the factorial of each individual digits is 122, which is not the same as the original number 151. It is not a Krishnamurthy number.

C Program to Check the Number is Krishnamurthy Number or not

Program description:- Write a C program to check the number is Krishnamurthy Number or not. Take input from the user.

Algorithm

1. Using one temporary variable temp, store a copy of the original number.
2. Initialize the variable sum with zero. It will store the sum of the factorial of each individual digit.
3. Using loop until temp is not equal to zero,
   3.a) Get the last digit of variable temp, and store it in the variable currentDigit.
   3.b) Calculate the factorial of variable currentDigit.
   3.c) Add the factorial result into the variable sum.
   3.d) Remove the last digit of the number.
4. Compare the original number with the value of the variable sum. If both are equal then the number is Krishnamurthy Number, else it is not.

C program to check Krishnamurthy Number

#include<stdio.h>
int main()
{
  int number, temp, sum, currentDigit, fact;
  printf("Enter an Integer: ");
  scanf("%d",&number);
  temp = number;
  sum = 0;

  while(temp!=0)
  {
    currentDigit = temp % 10;
    fact = 1;

    // finding factorial of the currentDigit
    for(int i=1; i<=currentDigit; i++)
    {
      fact *= i;
    }

    sum += fact;
    temp /= 10;
  }

  if(sum == number)
  {
    printf("%d is Krishnamurthy Number.",number);
  }
  else
  {
    printf("%d is not a Krishnamurthy Number.",number);
  }

  return 0;
}

Output for the different test-cases:-

Enter an Integer: 145
145 is Krishnamurthy Number.

Enter an Integer: 99
99 is not a Krishnamurthy Number.

Enter an Integer: 40585
40585 is Krishnamurthy Number.

Any number % 10 gives the last digit of the number and number / 10 removes the last digit of the number. You can find more details to find the last digit of the number, remove the last digit of the number. To write this program you should know, how to write a program to calculate the factorial of a number. In this program, we calculate factorial using for loop.

C Program to Print All the Krishnamurthy Numbers from 1 to N

Program description:- Write a program to print all the Krishnamurthy numbers in a range. Take range from the end-user. Use two functions, one for checking the number and another for finding factorial of digits.

#include<stdio.h>
void checkNumber(int);
long factorial(int);

int main()
{
    int range;
    printf("Enter range (>1): ");
    scanf("%d",&range);
    printf("Krishnamurthy Number, 
       in the range from 1 to %d are:\n", range);

    for(int i=1; i<=range; i++)
    {
      checkNumber(i);
    }
    return 0;
}

void checkNumber(int number)
{
   int temp, currentDigit;
   long sum = 0;
   temp = number;
   while(temp!=0)
   {
     currentDigit = temp % 10;
     sum += factorial(currentDigit);
     temp /= 10;
   }
   if(sum == number) printf("%d\t",number);
}

long factorial(int digit)
{
   long fact = 1;
   for(int i = 1; i<=digit; i++)
   {
     fact *= i;
   }
   return fact;
}

Output for the different test-cases:-

Enter range (>1): 1000
Krishnamurthy Number, in the range from 1 to 1000 are:
1 2 145

Enter range (>1): 10000000
Krishnamurthy Number, in the range from 1 to 10000000 are:
1 2 145 40585

In this program, two functions are used. The function checkNumber check every number within the range and another function factorial calculates the factorial of every digit.

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