So before moving directly on the writing program, I will recommend you please first know :

Page Contents

## What is Armstrong Number?

- Armstrong Number is also known as narcissistic number.
- A number which have n digits can be say that Armstrong number if its sum of nth powers of its digits is equal to original number.
- Like Armstrong number of 3 digits is a number which is equal to the sum of cube of its digits.
- For eg: 153, 370 etc.

**Example of Armstrong number**

Lets see it practically by calculating it,

Suppose I am taking 153 for an example

First calculate the cube of its each digits

1^3 = (1*1*1) = 1

5^3 = (5*5*5) = 125

3^3= (3*3*3) = 27

Now add the cube

1+125+27 = 153

It means 153 is an Armstrong number.

Ok, Then move on the program where your concept will be cleared 🙂

## C Program to check a number is Armstrong or not

```
#include<stdio.h>
#include<math.h>
#include<conio.h>
void main(){
int number,i=0,n,result=0,number1,temp;
printf("enter the number:");
scanf("%d",&number);
number1=number;
temp=number;
while(number!=0){
number=number/10;
i++;
}
while(number1!=0){
n=number1%10;
result=result+pow(n,i);
number1=number1/10;
}
if(temp==result)
printf("number is armstrong");
else
printf("not a armstrong");
getch();
}
```

**Output:**

## Explanation of Armstrong number validating program in c

- In the above program, you can see that I have Math.h header file because We need pow() function to calculate power and this function is defined in Math.h header file.
- Here I have taken almost six variable because in most of cases, we need to persist the previous value for the validation purpose.
- So first, I have taken input from the user and stored it in the ‘number’ variable.
- Now again, I am assigning the same variable in the ‘temp’ and ‘number1’ variable.
- First, while a loop is used to calculate the count of digits in a given number, we will use this count to calculate the power of each digit.
- And Second While loop is responsible for calculating the power of each digit and adding them together.
- Now, at last, we have if statement which I have used to validate our result after the performing operations.
- Using this if statement we are validating our original number(stored in ‘temp’ variable) is equal or not to calculated result ( stored in ‘result’ variable).
- Its value of temp and result is equal. It means that number is an Armstrong, and if not equal, then it is not an Armstrong number.

I hope now you have an idea of how to calculate and write a program to check number is an Armstrong or not in C.

## Also Prepare C interview programs given below

### C Questions on number

- Write a program to reverse an integer in C.
- Write a program in C to check whether an integer is Armstrong number or not.
- Write a program in C to print the fibonacci series using recursive method.
- Write a program in C to check whether a number is palindrome or not using recursive method.
- Write a program in C to add two integer without using arithmetic + operator.