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

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

What is the largest prime factor of the number 600851475143 ?

Here is the Java code using BigInteger to represent the given number.

package projecteuler; import java.math.BigInteger; /** * * @author Vasanth Raja Chittampally */ public class ProjectEuler { public static void main(String[] args) { BigInteger bi=new BigInteger("600851475143"); int div=7; while(bi.compareTo(new BigInteger("1"))!=0) { while(bi.mod(new BigInteger(div+"")).compareTo(new BigInteger("0"))==0) { bi=bi.divide(new BigInteger(div+"")); } div+=2; } System.out.println(""+div); } }

I tested the above code using Java. The answer it gives is 6857. It does take less than 1sec of execution time.

Hy!

Thanks the nice solution! Can you tell me which Primality test did you use? I tried many of them, but my applications were too slow!

I copy your code but my answer is 6859. why?