timeout - Java Prime Factorization: Program timing out? -

before blasted not following rules, did utilize search function , see there multiple threads on exact problem. however, none of them answered specific question.

i'm working on euler problem #3, need find highest prime factor of 600851475143. i don't need solving problem. have made brute force method (could better, know) solving it.

the program returns correctly of tests did smaller numbers (7 digits , less). however, when enter 600851475143 long input, program never gives me return. number big entered? causing happen? thought because using int tags instead of long, changing didn't alter result.

i'm sure simple , i'm missing it, curious what's happening. thank in advance :)

//euler 3: largest prime factor import java.io.*; import java.util.scanner; import java.lang.math;   public class euler3  {     public static void main(string[] args)     {         scanner scn = new scanner(system.in);          system.out.println("enter number!");         // create scanner         long numberinput=scn.nextlong();         //can't have factor higher it's square root         double limit=math.floor(math.sqrt(numberinput));         // system.out.println(limit);          //start testing highest number possible         for(long i=(numberinput-1);i>0; i--)         {             if(numberinput%i==0)                  system.out.println(i+" prime: "+isprime(i));          }      } //end main       public static boolean isprime(long n)      {         //check if n multiple of 2         if (n%2==0) return false;         //if not, check odds         for(int i=3;i*i<=n;i+=2)         {             if(n%i==0)                 return false;         }         return true;     } }    

to verify if number prime or not, use sieve of eratosthenes, run faster compared naive isprime method. won't provide implementation hint due phrase: i don't need solving problem.

also, there other hints missed. recommend review problem statement:

what largest prime factor