^^^ Absolutely.Make sure you mark it "principal payment only". Otherwise the bank will do one of a couple of things -- which I don't feel like typing our right now -- but it amounts to them making sure the payment is applied in a manner so that they can make the most money off you as they can.
Find an online calculator. You will be FLABBERGASTED at how much you will save yourself by paying your mortgage off early.
And I'd say, be sure to check your mortgage balance too.
Make sure those "illegitimate children" at the bank didn't record your additional principal payment incorrectly.
By accident I'm sure.