# C program to find prime factors of a number

The prime factors of a number are the factors which are prime numbers. For example, if we consider the number be 10 then factors of that number are 1, 2, 5 and 10. Among all the numbers 2 and 5 are the prime factors of 10. So prime factors of any number are the factors of that number which are prime. This program finds the prime factors of a given number by finding the factors of that number and then checking whether that is prime or not.

# Source Code :

#include<stdio.h> #include<stdbool.h> bool isPrime(int); int main(void) { int n, d=2; printf("\n Enter the Number: "); scanf("%d",&n); //Step 1 printf("\n Prime factors of %d is....\n",n); for(d=2;d<=n/2;++d) if(n%d==0 && isPrime(d)) //Step 2 printf("%d ",d); // Step 4 return 0; } bool isPrime(int x) //Step 3 { int d; for(d=2;d<=x/2;++d) if(x%d==0) return false; return true; }

# Sample Test cases :

1. Enter the Number: 10 Prime factors of 10 is.... 2 5 2. Enter the Number: 9 Prime factors of 9 is.... 3

# Explanation:

Step 1: The number is read from the user using scanf() function.

Step 2: The factors of a number are found using n%d and checked whether that factor is prime or not using ‘isPrime()’ function.

Step 3: isPrime() function returns true if given factor is prime number otherwise it returns false.

Step 4: Finally the factors which are prime numbers are printed on the output screen using printf() function.

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