448
Pioneering internet messenger ICQ shuts after 28 years - CNA
(www.channelnewsasia.com)
This is a most excellent place for technology news and articles.
I'm not sure how the numbers were doled out, but in 2000 it was a big deal having a sub-9-digit ICQ number.
Maybe I'm off by a bit then. I could have sworn I had one in like the 500k range but it must have been around '97 or '98.
I got on ICQ in 97 or 98 to keep up with friends from a MUD and mine was 7 digits. I haven't logged into it in over a decade because when I went back to see if anyone from the old game was around none ever showed up online.