How can my calculator be fixed after water damage?
In your case, since more than a month has passed, the calculator may be irreparably damaged, but if you have an hour or so to spare you may try to take your calculator apart and carefully clean it. You can use denatured alcohol and a small brush to remove any crud (especially greenish crud which is a sure sign of corrosion). Pay particular attention to the battery compartment and the connectors that feed power from the batteries to the electronics. Wipe off excess alcohol with tissues, and let the parts sit for a while to dry out. Then reassemble the calculator, pop in a fresh set of batteries and see if it will come back to life.
How to Fix Or Save Your Laptop After Water Damage With Uncooked Rice
This write up is brilliant. It talks about how rice can be used to dry your laptop soaked with water. Truly amazing!!