I don't know how many iPhones Apple sold. I don't even have rumors to go off other than the general feeling that the numbers must be pretty high.
But if Apple sold half a million to a million in the first two days, and it's now been close to a month of nearly perfect reviews, the number has to be pretty high. I say Apple hits (or nears) 3 million sales in 3 weeks. They will announce on the 20th.
Which isn't to say that 2 million or even 1 million would be a disappointment The smart phone market isn't very large, so Apple can (and will) get over 25% and then 50% marketshare pretty quickly.
The only real question is how high these initial numbers can go. I'm fully ready to eat crow, but I think 3 million is possible.
But only for Apple. No one else knows how to make a phone. They've proven as much over the last decade.