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Decision Making and Loops
Check Whether a Number is Even or OddCheck Whether a Character is a Vowel or ConsonantFind the Largest Number Among Three NumbersFind the Roots of a Quadratic EquationCheck Leap YearCheck Whether a Number is Positive or NegativeCheck Whether a Character is an Alphabet or notCalculate the Sum of Natural NumbersFind Factorial of a NumberGenerate Multiplication TableDisplay Fibonacci SequenceFind GCD of two NumbersFind LCM of two NumbersDisplay Characters from A to Z Using LoopCount Number of Digits in an IntegerReverse a NumberCalculate the Power of a NumberCheck Whether a Number is Palindrome or NotCheck Whether a Number is Prime or NotDisplay Prime Numbers Between Two IntervalsCheck Armstrong NumberDisplay Armstrong Number Between Two IntervalsDisplay Factors of a NumberMake a Simple Calculator Using switch...casePrint Pyramids and Patterns
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Demonstrate the Working of Keyword longDisplay Prime Numbers Between Intervals Using FunctionCheck Prime or Armstrong Number Using User-defined FunctionCheck Whether a Number can be Expressed as Sum of Two Prime NumbersFind the Sum of Natural Numbers using RecursionFind Factorial of a Number Using RecursionFind G.C.D Using RecursionConvert Binary Number to Decimal and vice-versaConvert Octal Number to Decimal and vice-versaConvert Binary Number to Octal and vice-versaReverse a Sentence Using Recursioncalculate the power using recursion
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C Program to Check Armstrong Number

To understand this example, you should have the knowledge of the following C programming topics:

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


              

abcd... = an + bn + cn + dn +

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

Check Armstrong Number of three digits


              

#include <stdio.h>
int main() {
    int num, originalNum, remainder, result = 0;
    printf("Enter a three-digit integer: ");
    scanf("%d", &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)
        printf("%d is an Armstrong number.", num);
    else
        printf("%d is not an Armstrong number.", num);

    return 0;
}

Output


              

Enter a three-digit integer: 371
371 is an Armstrong number.

Check Armstrong Number of n digits


              

#include <stdio.h>

int main() {
    unsigned long long int num, originalNum, remainder, n = 0;
    unsigned long long int result = 0;

    printf("Enter an integer: ");
    scanf("%llu", &num);

    originalNum = num;

    // store the number of digits of num in n
    while (originalNum != 0) {
        originalNum /= 10;
        ++n;
    }

    originalNum = num;

    while (originalNum != 0) {
        remainder = originalNum % 10;

        // calculate remainder^n
        unsigned long long int power = 1;
        for (unsigned long long int i = 0; i < n; i++) {
            power *= remainder;
        }

        result += power;
        originalNum /= 10;
    }

    // if num is equal to result, the number is an Armstrong number
    if (result == num)
        printf("%llu is an Armstrong number.\n", num);
    else
        printf("%llu is not an Armstrong number.\n", num);

    return 0;
}

Output


              

Enter an integer: 1634
1634 is an Armstrong number.

In this program, the number of digits of an integer is calculated first and stored in n. And, we compute the power of individual digits in each iteration of the second for loop.