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# (C++ programming Example for Beginners)

# C++ Program to Check Armstrong Number

#### In this example, you will learn to check whether a number entered by the user is an Armstrong number or not.

A positive integer is called an Armstrong number (of order n) if

abcd... = a^{n}+ b^{n}+ c^{n}+ d^{n}+ ...

In the case of an Armstrong number of 3 digits, the sum of cubes of each digit is equal to the number itself. For example, 153 is an Armstrong number because

153 = 1*1*1 + 5*5*5 + 3*3*3

## Example: Check Armstrong Number of 3 Digits

```
#include <iostream>
using namespace std;
int main(){
int num, originalNum, remainder, result = 0;
cout << "Enter a three-digit integer: ";
cin >> num;
originalNum = num;
while (originalNum != 0) {
// remainder contains the last digit
remainder = originalNum % 10;
result += remainder * remainder * remainder;
// removing last digit from the orignal number
originalNum /= 10;
}
if (result == num)
cout << num << " is an Armstrong number.";
else
cout << num << " is not an Armstrong number.";
return 0;
}
```

**Output**

Enter a positive integer: 371 371 is an Armstrong number.

In the program, we iterate through the while loop until `originalNum` is 0.

In each iteration of the loop, the cube of the last digit of `orignalNum` is added to `result`.

```
remainder = originalNum % 10;
result += remainder * remainder * remainder;
```

And, the last digit is removed from the `orignalNum`

.

When the loop ends, the sum of the individual digit’s cube is stored in `result`.

## Example: Check Armstrong Number of n Digits

```
#include <cmath>
#include <iostream>
using namespace std;
int main(){
int num, originalNum, remainder, n = 0, result = 0, power;
cout << "Enter an integer: ";
cin >> num;
originalNum = num;
while (originalNum != 0) {
originalNum /= 10;
++n;
}
originalNum = num;
while (originalNum != 0) {
remainder = originalNum % 10;
// pow() returns a double value
// round() returns the equivalent int
power = round(pow(remainder, n));
result += power;
originalNum /= 10;
}
if (result == num)
cout << num << " is an Armstrong number.";
else
cout << num << " is not an Armstrong number.";
return 0;
}
```

**Output**

Enter an integer: 1634 1634 is an Armstrong number.

In this program, the number of digits of the entered number is calculated first and stored in `n`.

And, the `pow()`

function computes the power of individual digits in each iteration of the `while`

loop.

Disclaimer: The information and code presented within this recipe/tutorial is only for educational and coaching purposes for beginners and developers. Anyone can practice and apply the recipe/tutorial presented here, but the reader is taking full responsibility for his/her actions. The author (content curator) of this recipe (code / program) has made every effort to ensure the accuracy of the information was correct at time of publication. The author (content curator) does not assume and hereby disclaims any liability to any party for any loss, damage, or disruption caused by errors or omissions, whether such errors or omissions result from accident, negligence, or any other cause.The information presented here could also be found in public knowledge domains.