Yeah . . . it has 7 (up to 8, technically, but 7 for all intents and purposes.), though 1 is reserved for OS activity so game developers only have 6 at their disposal. I don't know what Tommy is smoking, but both the 360 and the PS3 are clocked at 3.2 GHz, not 4.2. Also, they are wildly different chip architectures, so clock speed is really only of secondary importance when comparing the chips. The cores of the Xbox 360 work much differently than the cores of the PS3 from what I understand. You certainly could not conclude that the PS3 is anything like twice as powerful as the 360 based on the fact that it has 7 cores versus the 360's 3 cores. Additionally, while the PS3 seems to have the better processor of the two, the 360 has twice as much RAM which balances things out a bit.
edit: SP beat me to the punch.