I have a hybrid bike with 622 x 19 rims on it. I want to put mountain bike tires on so I can ride trails. But I can't find knobby tires to fit the wheels. So I want to get new a wheel set.

Is 622 equivalent to a 29" mountain bike rim?

Can I put 26" wheels on it without getting new brakes?

It looks like the frame will fit wider tires, so that's not what i'm worried about right now.