User blog comment:Legionwrex/I figured out how many Reapers there are!/@comment-4953843-20120801020755/@comment-1221773-20120801042332

Actually, there are multiple sources throughout the lore (including dialogue with some characters) indicating that the galactic population is in the trillions, and that Citadel space alone is populated by "dozens" of other spacefaring races besides those we know. In effect, the ME games only allow us a very limited glimpse of the known galaxy.