The xkcd comic #247 "Factoring the Time" shows one of the characters trying to calculate prime factors of the current time on a digital clock. I liked the idea to build a clock that shows time as prime factors, preferably by means of LEDs which represent the given factors. For readability I decided to display hours and minutes separately.
In the grand scheme of things I see this clock as a potential frontend for my modular whistwatch idea, if it ever happens.
As of now, the clock is only existant as a prototype in Processing (I used version 2.1). I have done two versions: one with hour and minutes, one with hours, minutes and seconds.
The version with seconds reveals the fact, that it is actually a clock better. Feel free to download and use the prototypes. The are not especially pretty but a fun way to tell time.