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

## 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. Read more about prime factors.

## 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. But before I formally state the logic. It is recommended that you must know below concepts.

Below is the step by step descriptive logic to find prime factors.

- Read 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 n/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; /* * Read 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; }

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 > (Remove spaces from pre and code tags)