Not that many. No matter how you define them, there are millions fewer now than there were in 1939, and it's not likely we'll ever get back to that number, not this century, anyway.
Sergio Della Pergola and colleagues have published their annual Jewish demographic report, which seems, at first glance, to be quite interesting, especially if you like demography.
If one counts people for whom being Jewish has any significance, the largest Jewish community is in Israel. It's also the only sizable community which is growing.