Numberwang

http://www.youtube.com/watch?v=qjOZtWZ56lc

You might describe this as "The Numberwang Code".

Installation

gem install numberwang

require "numberwang"

OR... In Rails, just insert this into your Gemfile:

gem "numberwang"

Use

1.numberwang?

=> true

1.7.numberwang?

=> false

etc.