Write a C program to enter any number and find Prime factors of the given number. C program to list all prime factors of a given number. Logic to print prime factors of any given number in C program.

**Example**

**Input**

Input any number: 10

**Output**

Prime factors of 10: 2, 5

## Required knowledge

Basic C programming, If else, For loop

Must know -

### What is Prime factor?

Factors of any number that are prime numbers are called as Prime factors of that number. For example: 2 and 5 are the prime factors of 10.

## Logic to check prime factors of a given number

Let us learn the logic to find prime factors. I have divided the logic in three simple steps. Below is the step by step descriptive logic to find prime factors.

- Input a number from user. Store it in some variable say num.
- Run a loop from 2 to num/2, incrementing 1 in each iteration. The loop structure should look like for(i=2; i<=num/2; i++). You may think why loop from 2 to num/2? Because prime number starts from 2 and any factor of a number is always less than num/2.
- Inside the loop check if i is a factor of num or not. If it is a factor then check it is prime or not. If i is factor and is prime then you got one prime factor of num.

## Program to find prime factors of any number

```
/**
* C program to find all prime factors of a given number
*/
#include <stdio.h>
int main()
{
int i, j, num, isPrime;
/*
* Input a number from user
*/
printf("Enter any number to print Prime factors: ");
scanf("%d", &num);
printf("All Prime Factors of %d are: \n", num);
/*
* Find all Prime factors
*/
for(i=2; i<=num; i++)
{
/*
* If i is a factor of num
*/
if(num%i==0)
{
/*
* If i iss Prime or not
*/
isPrime = 1;
for(j=2; j<=i/2; j++)
{
if(i%j==0)
{
isPrime = 0;
break;
}
}
/*
* If i is Prime factor of num
*/
if(isPrime==1)
{
printf("%d, ", i);
}
}
}
return 0;
}
```

Output

Enter any number to print Prime factors: 15 All Prime Factors of 15 are: 3, 5,

Happy coding 😉

### Recommended posts

- Loop programming exercises index.
- C program to print prime numbers between 1 to n.
- C program to find sum of prime number in given range.
- C program to find prime numbers between given interval using functions.
- C program to check Armstrong number.
- C program to check Perfect number.
- C program to check Strong number.

<pre><code> ----Your Source Code---- </code></pre>