Thursday, 22 June 2017 12:47

## Armstrong Number in C++

Written by
Rate this item

Before going to write the C++ program to check whether the number is Armstrong or not, let's understand what is Armstrong number.

Armstrong number is a number that is equal to the sum of cubes of its digits. For example 0, 1, 153, 370, 371 and 407 are the Armstrong numbers.

Let's try to understand why 371 is an Armstrong number.

1. 371 = (3*3*3)+(7*7*7)+(1*1*1)
2. where:
3. (3*3*3)=27
4. (7*7*7)=343
5. (1*1*1)=1
6. So:
7. 27+343+1=371

Let's see the C++ program to check Armstrong Number.

1. #include <iostream>
2. using namespace std;
3. int main()
4. {
5. int n,r,sum=0,temp;
6. cout<<"Enter the Number=  ";
7. cin>>n;
8. temp=n;
9. while(n>0)
10. {
11. r=n%10;
12. sum=sum+(r*r*r);
13. n=n/10;
14. }
15. if(temp==sum)
16. cout<<"Armstrong Number."<<endl;
17. else
18. cout<<"Not Armstrong Number."<<endl;
19. return 0;
20. }

Output:

```Enter the Number= 371
Armstrong Number.
```
```Enter the Number= 342
Not Armstrong Number.	``` 