This is pretty fascinating, do you know of any good sites or books which will get me up to scratch on different number systems? I haven't studied math in a long

This is pretty fascinating, do you know of any good sites or books which will get me up to scratch on different number systems? I haven't studied math in a long time, so do you think it would be worth going over the basics, like calculus and geometry, again to build a foundation before venturing so far out?