The Koran does not mention "72 virgins," not a single time. That idea comes from Islamic traditions, a tradition which which is in dispute by many Muslims. The folks here who have the strongest opinions on this don't actually appear to have read the Koran (cover to cover). Why not take the time? It is not a long book, though certainly boring and tedious. Heaven is described in rather sensual terms in the Koran (as a place where people recline on couches) but 72 virgins is never mentioned.
Right, it's 72 raisins.