A while back, I remember reading an article, saying ~360 is enough. Please note, a nuclear carpet bombing is not necessary. As long as you destroy all the cities and people, all the military bases, all the precious natural resources(like oil), all the nuclear reactors(chain reaction),...... you can leave some African tribes alone, they are in the stone age anyways. [ March 11, 2002: Message edited by: Don Liu ]
I don't know in real life, but I think the radiation is going to kill more people than the explosion! At least one novelist, Nevil Schute, in his great work, 'On the Beach' predicts how disastrous it could be! In Australia, waiting for the radiation clouds to rain over you - You have choice though - The State has supplied a red Cyanide capsule to every one. Just to make the inevitable death quicker than radiation. With instruction to consume it when effects of radiation appear on you!!