# Armstrong Number C Program

By | September 17, 2015

Let us understand what is an ArmstrongInteger Series and let us learn how we can implement Armstrong Number in C programming language.

#### What is an Armstrong Number Series?

An Armstrong number is the sum of cubes of the individual digits of the number. If the sum of the digits is equal to the number, then it is said to be an Armstrong Integer.

An Armstrong integer is similar to a narcissistic number. However, there’s a difference between an Armstrong number and narcissistic number.

An Armstrong integer is essentially a 3 digit number whereas a narcissistic number is a 4 or more than 4 digit number. It is also usually regarded as 4 digit Armstrong Number.

#### Example

153 = (1 * 1 * 1) + (5 * 5 * 5) + (3 * 3 * 3)
371 = (3 * 3 * 3) + (7 * 7 * 7) + (1 * 1 * 1)

Armstrong numbers are essentially 3 digit integers. However, if you intend to calculate 4 digit armstrong number in C programming, you need to check the narcissistic number c program.

#### Algorithm For Armstrong Number in C Programming

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#### Armstrong Series Logic Explanation

1. The input value is copied into a temporary variable.
2. The last digit of the input value is extracted, cubed and added to the sum variable.
3. The last digit is extracted till the input value is not equal to zero.
4. After the process is completed and the remainder is zero, the sum variable is compared with the temporary variable.
5. If the sum and temporary variables are equivalent, the input value is an Armstrong Number, else it is not an Armstrong Integer.

Note: This C program for Armstrong Numbers is compiled with GNU GCC compiler on Linux Ubuntu 14.04 operating system. However, these codes are compatible with all other operating systems.

Must Read: C Program To Check Palindrome Numbers

#### Method 1: C Program To Find Armstrong Numbers using While Loop

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Must Read: Tribonacci Series C Program

#### Method 2: Generate Armstrong Numbers in C Programming using For Loop

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Must Read: C Program To Check if a Number is Magic Number or Not

#### Method 3: C Program To Check Armstrong Number using Function

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Must Read: C Program To Check Strong Numbers

#### Output

Let’s discuss more on Armstrong number in C programming in the comment section below if you have any compilation errors and any doubts about the same.

## 32 thoughts on “Armstrong Number C Program”

1. Pankaj Dhende

I am getting confused in void main and int main. The armstrong number programs that are here jave int main() declarations. Is it compulsory to use them?

1. Tushar Soni Post author

Hi Pankaj! int main() is primarily used when you want to fetch arguments using Command Line. Otherwise, void main() will work. This Armstrong Number C Programs above can be made to work through command line by adding two arguments in the main function. (int argc, int *argv).

In this Armstrong Integer Program, I am getting confused with the modulus operator. Can you help me understand the use of Modulus Operator?

1. Dipak Kale

This is just awesome. So many ways to write armstrong number program in c! It helped me to clear my concepts functions and also how to convert for loop into while loop.

1. Tushar Soni Post author

Hi Rajendra. Well, the float variables cannot be used an an operand with Modulus Operator. That is why you would be getting errors. Please check which datatypes work with Modulus Operator and then select a suitable datatype.

4. Pankaj Pawar

Why not use Recursion to calculate Armstrong Numbers,

5. Rab Khan

I think the condition num!=0 can also be changed to num>0 or num>=1 in this code.

while(num1 != 0)
{
rem = num1%10;
sum = sum + (rem*rem*rem);
num1 = num1/10;
}

6. Aarav Rathod

Why do we need to copy the armstrong number variable num1 into temp? I also see that the sum variable os compared to temp. Why can’t we compare it to num1 variable?

How do I cube the remainder variable? Is there a built in function for it or do we have to make a user defined function?
for(temp = num1; num1 != 0;)
{
rem = num1%10;
sum = sum + cube(rem);
num1 = num1/10;
}

8. Chandu

Can we get possible number of Armstrong numbers within a range? Ex,if input is 10 ,10 Armstrong numbers should be output?

1. Damodar Das

Yes. You may have to add a For loop and run it till the ending limit of your range.

9. Tushar Soni Post author

Hi Rahul. It is GCC Compiler(Linux Ubuntu’s default C Compiler) with the gEdit editor (Linux Ubuntu’s default text editor).

10. princess park

How do I do this using a recursive function?

11. Vamshi NCH

So, as far as I understood is that Armstrong number is a 3 digit number and the 4 digit armstrong number is a narcissistic number. Please correct me if I am wrong!

12. Gaurav Saraswat

Hi tushar
Can u plz explain why the sum in the if statement is not equalized to num1 in method 2 using for loop?Rather it is equalized to temp. Plz explain

1. Tushar Soni Post author

When you perform: num1 = num1/10, the original num1 gets modified. So, you cannot compare the sum variable with the modified value. Hence, we are using temp variable to check whether the original num1 is equal to sum or not.

1. Tushar Soni Post author

Okay! No problem! Bade bade deshon mein aisi choti choti galtiyaan hoti rehti hai! 😉