I'd say the number is at least capped at about 100 billion, but that depends on how tightly you define "person" and "place" (not even getting into the specifics of "autistic").

E.G. if you want your instances of "people" to be active, we're now capped at roughly 8 billion, since 92% of instances have already been garbage collected in this run.

I would still recommend planning a Long integer, just to get yourself some room for error.