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Program to check a number is Armstrong or not
In this program, we will find the number is Armstrong or not where the number should be entered by the user, we will look at different ways to write Armstrong number in C.
Most websites have given incorrect definitions/codes for Armstrong of a number.








Very Important
On most websites, Armstrong number definition is given wrong. They all assume any number where the sum of the cubes of its digits is equal to the number itself is Armstrong Number.
However, Armstrong number is any number following the given rule –
- abcd… = an + bn + cn + dn + …
- Where n is the order(length/digits in number)
Example 1
Example = 153 (order/length = 3)
153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153
153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153
Example 2
Example = 1634 (order/length = 4)
1634 = 1^4 + 6^4 + 3^4 + 4^4 = 1 + 1296 + 81 + 256 = 1634
1634 = 1^4 + 6^4 + 3^4 + 4^4 = 1 + 1296 + 81 + 256 = 1634












C Code:-
#include <stdio.h> #include <math.h> // Armstrong number is any number following the given rule // abcd... = a^n + b^n + c^n + d^n + ... // Where n is the order(length/digits in number) // Example = 153 (order/length = 3) // 153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153 // Example = 1634 (order/length = 4) // 1634 = 1^4 + 6^4 + 3^4 + 4^4 = 1 + 1296 + 81 + 256 = 1634 // number of digits in a number is order int order(int x) { int len = 0; while (x) { len++; x = x/10; } return len; } int armstrong(int num, int len){ int sum = 0, temp, digit; temp = num; // loop to extract digit, find power & add to sum while(temp != 0) { // extract digit digit = temp % 10; // add power to sum sum = sum + pow(digit,len); temp /= 10; }; return num == sum; } // Driver Code int main () { int num, len; printf("Enter a number: "); scanf("%d",&num); // function to get order(length) len = order(num); // check if Armstrong if (armstrong(num, len)) printf("%d is Armstrong", num); else printf("%d is Not Armstrong", num); }
Output:-
Enter a number: 1634
1634 is Armstrong
Enter a number: 209
209 is Not Armstrong
Enter a number: 153
153 is Armstrong








Method 2
This method uses recursion in C
Code
#include<stdio.h> #include <math.h> int order(int x) { int len = 0; while (x) { len++; x = x/10; } return len; } int getArmstrongSum(int num, int order){ if(num == 0) return 0; int digit = num % 10; return pow(digit, order) + getArmstrongSum(num/10, order); } // Driver Code int main () { int num, len; printf("Enter a number: "); scanf("%d",&num); // function to get order(length) len = order(num); // check if Armstrong if (num == getArmstrongSum(num, len)) printf("%d is Armstrong", num); else printf("%d is Not Armstrong", num); }
Output
Enter a number: 1634 1634 is Armstrong
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