Project Euler #3 in Ruby solution times out -

i'm going through few of project euler problems practice problem solving using ruby. came following solution problem 3, , while works smaller numbers, never seems return value larger numbers. because of bignum? can describe me why it's timing out, , better way solve problem (preferably reasoning/info on what's going on behind scenes. i'm trying understand)

project euler problem:

the prime factors of 13195 5, 7, 13 , 29. largest prime factor of number 600851475143 ?

my solution:

def primecheck(number)   (2...number).each { |x| return false if number % x == 0}   true end  def largestprime(number1)   factors = []     (1..number1).each |i|       if number1 % == 0 && primecheck(i)         factors <<       end     end puts "the answer #{factors.last}" end  largestprime(600_851_475_143) 

hint: once you've found prime factor, can divide it. reduces range of remaining potential divisors have check.

using first example:

13195/5 = 2639, 2639/7  = 377, 377/13  = 29, 29/29   = 1, done. 

this way, had check 29 instead of way 13195.

there ways improve further, optimization alone should more enough simple problem.