C Exercises: Check two numbers are Amicable numbers or not

Last update on March 19 2025 12:39:12 (UTC/GMT +8 hours)

25. Amicable Numbers Pair Check Variants

Write a program in C to check whether two numbers are Amicable numbers or not.

Sample Solution:

C Code:

# include <stdio.h>
# include <stdlib.h>
# include <stdbool.h>
# include <math.h>

// Function to find the sum of proper divisors of a number 'n'
int ProDivSum(int n)
{
    int sum = 1;
    for (int i = 2; i <= sqrt(n); i++) // Loop to find divisors of 'n'
    {
        if (n % i == 0)
        {
            sum += i; // Adding divisor 'i' to the sum
            if (n / i != i)
                sum += n / i; // Adding the corresponding divisor to the sum
        }
    }
    return sum; // Returning the sum of divisors
}

// Function to check if two numbers 'a' and 'b' are Amicable pairs
bool chkAmicable(int a, int b)
{
    return (ProDivSum(a) == b && ProDivSum(b) == a); // Checking if the sums of divisors of 'a' and 'b' match each other
}

// Main function
int main()
{
    int nm1, nm2; // Variables to store the input numbers

    // Printing information about the program and asking for user input
    printf("\n\n Check whether two numbers are Amicable pairs or not: \n");
    printf("\n Sample: (220, 284), (1184, 1210), (2620, 2924).. \n");
    printf(" --------------------------------------------------------\n");
    printf(" Input the 1st number : ");
    scanf("%d", &nm1);
    printf(" Input the 2nd number : ");
    scanf("%d", &nm2);

    if (chkAmicable(nm1, nm2)) // Checking if 'nm1' and 'nm2' are Amicable pairs using the function
        printf(" The given numbers are an Amicable pair.\n"); // Printing if the numbers are an Amicable pair
    else
        printf(" The given numbers are not an Amicable pair.\n"); // Printing if the numbers are not an Amicable pair

    return 0; // Returning 0 to indicate successful execution
}

Sample Output:

 Input the 1st number : 1184                                                                                  
 Input the 2nd number : 1210                                                                                  
 The given numbers are an Amicable pair.

Visual Presentation:

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C program to check if two numbers form an amicable pair and display their proper divisor sums.
• Write a C program to verify amicable pairs by calculating the divisor sums for each number.
• Write a C program to test amicability with optimized functions for repeated divisor sum calculations.
• Write a C program to compare multiple number pairs in an array to detect all amicable pairs.

C Programming Code Editor:

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