You can take a look at our contest thread - a part of long-time participants has accounts that start with number 2 or even 1. Account generated at the moment has number 4 at the beginning, and between those accounts millions of new users. You can check it yourself by creating one.
Foreseeing your question, yes, not all of them are active accounts, but still it requires a lot of time and people to generate so many IDs.

Those accounts are with us for years and still playing.