“Trillions” is probably a major lowball, coruscant alone officially a population in the trillions, and when you actually do the math making some estimates based on densely-populated cities on earth it’s more likely in the quadrillions.

And there’s million of inhabited planets, most not even close to as densely populated as coruscant of course, but there are a good handful of other ecumenopolises (ecumenopoli?) around the galaxy