* Florian Frank <flori / nixe.ping.de> [2005-06-22 05:40:14 +0900]:

>  def prime?
>    not (2..Math.sqrt(self).floor).find { |i| self % i == 0 }
>  end
> end

Have you tried skipping even numbers (excluding 2 of course)?
That should give you a little more speed.

-- 
Jim Freeze