Interesting airport numbers from the FAA's NASR datamabase:

FacilityType Count
AIRPORT 12641
BALLOONPORT 15
GLIDERPORT 34
HELIPORT 5413
SEAPLANE BASE 497
STOLPORT 80
ULTRALIGHT 135
Total 18815

That's 12875 air/gliderports alone!

In case you're wondering, 12675 of those have described runways.

The number of runways in the air/gliderports:
1 10391
2 1831
3 356
4 72
5 15
6 8
7 1
8 1

I wonder which airport has 8 runways?! (I am not going to check.)

2NO