You may run a query and find the username.
But keep in mind:
- it will not take into account of deleted posts etc
- if you have editd the database manually then it may give you incorrect answer.
- etc...
Code:
SELECT * FROM `post` WHERE `postid` = 2000000
Edited:
Or this will show you 2,000,000th row in the database.
Code:
SELECT * FROM `post` LIMIT 2000000 , 1
.