That's a Gedmatch Genesis ID number, from https://genesis.gedmatch.com/
. Genesis numbers start with two letters.
I found you on Gedmatch Genesis, so I confirmed that this is a valid number. But I'm puzzled, because your WikiTree profile shows your number as CH9214979...
At the moment, Gedmatch and Gedmatch Genesis don't talk to each other directly (and WikiTree links to Gedmatch don't work for these numbers), but that's expected to change.