Personally, I tend to define a friend as someone I could call at 3 a.m. if I needed to. Not that that's some sort of universal yardstick for friendship, of course. But by my own standards, I have one friend - my SO.
In terms of people who mean a lot to me and to whom I have reason to suspect that I mean something, too, there are a few more. In precise numbers, there are four such people who aren't quite friends by my own definition, but who are definitely more than acquaintances. They're somewhere in-between, I suppose.
Acquaintances that I meet/catch up with every once in a blue moon if and when I feel up to it - sometimes only once a year or less - half a dozen, I suppose.
To the best of my knowledge, and also in my own opinion, every last one of them is NT. But, I have needed my entire life to date to assemble this ecclectic group of people for whom I don't cease to exist because I'm not a social butterfly. And I have no reason to expect that we, or some of us, won't eventually drift apart again.
I'm a bit surprised at the numbers now - so many people! But these particular people are so uniquely tolerant of my idiosyncrasies and my need for frequent downtime that it doesn't feel like such a large (to me) social circle (and I mean that in a positive sense). Otherwise I wouldn't be able to cope.