I would actually say you could get away with 7 or 8, if you just went females. I have 6 and 3 corys in a 10g.
Honestly, I know a lot of people will say " lots of cover and hiding places ". These fish are not going to be constantly fighting. I have 2 pots, a rock, a fake plant, and a small coral decoration with the majority of the tank being just open swimming space. These females develop a very close bond, guarding the algae wafer from the corys while taking turns eating it, they all swim to the same are to get ready for food, no signs of aggression at all. The first few days to a week will be tough, but after that your really home free (unless its a female that turns male).