The article says there are 1 million buildings in NYC?

That seems high ... only 10 people per building?

Tons of buildings aren't residential. And there's still lots of single family homes as you get out into Queens, Staten Island, up further in the Bronx and further out in Brooklyn sometimes too.

I wonder how many people are living in buildings with 100+ people as I am (estimate a couple thousand in my building from back of napkin math I think).

New York City's fairly vast when you take into account Brooklyn, Queens, Staten Island and the Bronx. Manhattan's less than a tenth of the land area.

People forget a lot of NYC looks like this:

https://maps.app.goo.gl/ch4rPVXcMoxsBLDK6

The biggest buildings tend to have a residential population of approximately zero.

One million buildings…that's residential, commercial office or retail, and other (factories, storage, etc).