Division problems on 32bit OS

> I was happily doing some prime number detection until I came across some limits in my 32bit OSX 10.5 (7849431181 % 41) produces -1 which threw me then I read about it a little more if you want to tell if your php is running under 32bit OS try this: echo PHP_INT_MAX; // I get 2147483647 If your 32bit you get: 2147483647 If your 64bit like dreamhost servers are you get 9223372036854775807 That really confused me.