As indicated in Sinestro Corps Special (which I HIGHLY recommend.....there's a lot going on, including a major "break-through", so to speak) , there are 52 parallel earths in THIS universe, as well as 52 parallel UNIVERSES.

so what would that be, 52 x 52 x 52 = 140,608 earths? Are my calculations correct?

I don't really get this; shouldn't there just be one earth per universe? I mean, the earths are parallel by virtue of them being in parallel universes. Aren't they?

Imagine you have a Universe that likes to make cigarettes out of Earths, and it takes 52 Earths to make one cigarette. This Universe has 52 Earths and it has 51 friends with 52 Earths apiece. Oh heck, I forgot to tell you one is supposed to treat the Earths like cigarette butts. Look, forget it, this'll take too long; either way, the answer is always one more than you thought it was, so the correct answer would have been 53, if I'd even bothered to ask it properly.