scala won't take a 12-digit integer

ok so I'm just getting started in scala.. ran into a weird problem with a large number.

import Math._
var num:Long=0
num+=600851475
num*=1000
println(num)

that code works fine, yet the following doesn't compile with an error saying the integer is too large.

import Math._
var num:Long=0
num+=600851475000
println(num)

what's up? can scala not handle a 12-digit number? :/