Actually 666 does not represent the Devil. Back in Roman times, Nero Caesar was Emperor of Rome. He set Rome on fire, and in order for the citizens of Rome to not think it was him, he blamed Christians. The Christians were mostly killed although some recanted and forgot Christianity to save themselves. Anyways, in the language spoke back then, letters also corresponded to numbers. Nero Caesar's name corresponds with 666. That is where the number comes from. So really the Devil has nothing to do with it, it was just a way Christians identified Nero Caesar.