538342. Had a weak / compromised password for ages, I'm surprised to have been able to access my account and change to a stronger password. I'm not sure the popularity of 6 digit accounts and the password compromise times overlapped much though.

Had some great times chatting to people all around the world on ICQ. I think I still have a couple of FB friends from that era.

I was bouncing an idea of an IRC like pager app around in my head in the months before I became aware of ICQ (but well after it was already developed).