answer for eula project- problem3

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

What is the largest prime factor of the number 600851475143 ?

ANSWER

6857

JAVA CODE

import java.math.BigInteger;

public class PrimeFactor {

public static void main(String[]args){

BigInteger req=new BigInteger("600851475143");

primeGenerator(req);

}

private static void primeGenerator(BigInteger req) {

int max=775146;//sqrt of 600851475143

int ans=0;

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

boolean prime=true;

for (int i = 2; i <= (int)Math.sqrt(j); i++) {

if(j%i==0 )

prime=false;

}

if(prime){

BigInteger bi=new BigInteger(Integer.toString(j));

BigInteger mode=new BigInteger("0");

if(req.mod(bi).equals(mode) &&ans<j){

ans=j;

}

}

}

System.out.println("ans="+ans);

}

}