That's going to be a new tank 

@hsvhel That sucks.

I had a plumber recently for basically the same thing,  the threads were corroded.  

Most are not interested in a repair, swap it out and they're off.  That one may have had a 10 year warranty though, Rheem are good to deal with if you get in touch with them.

Can it be repaired, probably-  Is it economical to repair, probably not

Its stuffed, you will need a new one,

Folks had something similar a couple of months ago, leaking out of the outlet pipe,  They got a new one,

But the tank had a 10yr warranty so the manufacturer said they would take it back and check it for pin prick hols ( most likely in the welds on the outlet connection, - never did hear what the result was,,,

The extent of corrosion indicates its been leaking for a while,

Looks like I've dodged a bullet for now. The leak was in the pipe connection which some hemp seems to have fixed. While the top of the tank has suffered some corrosion, it will live to see another day (for now).