/*

* The prime factors of 13195 are 5, 7, 13 and 29.

*

* What is the largest prime factor of the number 600851475143 ?

*/

public class problem03 {

public static void main(String args[]) {

int test = 300;

long num = 600851475143L; // L designates it as a long

int root = (int)Math.floor(Math.sqrt(num)); // casting

// System.out.println(root);

for (long i = 1; i < num/2; i++) {

if (num%i == 0) {// if it's a factor of num

System.out.print(i + " is a factor of " + num + ". ");

if (isPrime(i) == true) {// if it's prime

System.out.println("And it's prime!");

}

}

}

}

public static boolean isPrime(long num) {

boolean prime = true;

int numroot =(int)Math.floor(Math.sqrt(num));

System.out.println("Testing " + num +" for primeness up to sqrt(" + num + ")");

for (int j=2; j<numroot; j++) {

if (num%j == 0) {

prime = false;

//System.out.println(num + " isn't prime");

}

}

return prime;

}

}