That value is in hex. Are you looking at that data through phpmyadmin? I guarantee you the value of 3736353631313938313338313135323639 is actually 76561198138115269 in the database. Which is this user:
http://steamcommunity.com/profiles/76561198138115269
My guess is that phpmyadmin is displaying the data incorrectly. I believe I told somebody how to fix it before, just search this thread for the word hex.
As for converting SteamID to SteamID64 or SteamID64 to SteamID, you can try out this MySQL stored procedure:
https://forums.alliedmods.net/showp...22860e3ade474c0dfcdaf&p=1593324&postcount=306
I would recommend doing that on a test database first before doing it on your production. This might work out for you. The only problem is, I'm assuming you'd manually have to use this each time you want to update your other table.
This addon does feature a template variable that does convert SteamID64 into SteamID, but you'd still have to get it into the database in someway. Unfortunately this addon uses SteamID64 as it's the only way to properly interface with the API.