By | 24.03.2017

# C Program to Find sum of proper divisors of number

Write a C Program to Find sum of proper divisors of natural number using Recursion. Here’s simple Program to Find sum of proper divisors of natural number using Recursion in C Programming Language.

## Recursion : :

• Recursion is the process of repeating items in a self-similar way. In programming languages, if a program allows you to call a function inside the same function, then it is called a recursive call of the function.
• The C programming language supports recursion, i.e., a function to call itself. But while using recursion, programmers need to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.
• Recursive functions are very useful to solve many mathematical problems, such as calculating the factorial of a number, generating Fibonacci series, etc.

## Problem : :

Given a natural number, calculate sum of all its proper divisors. A proper divisor of a natural number is the divisor that is strictly less than the number.

For example, number 20 has 5 proper divisors: 1, 2, 4, 5, 10, and the divisor summation is: 1 + 2 + 4 + 5 + 10 = 22.

Examples:

Input : n = 10
Output: 8
// proper divisors 1 + 2 + 5 = 8
Input : n = 36
Output: 55
// proper divisors 1 + 2 + 3 + 4 + 6 + 9 + 12 + 18 = 55

Below is the source code for C Program to Find sum of proper divisors of natural number using Recursion which is successfully compiled and run on Windows System to produce desired output as shown below :

### OUTPUT  : :

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