ERTO for 650c is 571mm IIRC.
THese are road bike wheels for smaller road bikes. They would probably fit into the frame but if you are using rim brakes you might not be able to adjust the brakes to a position that they will contact the rims. Also tyre choice is very limited (and very road orientated) for 650c. I would expect a 650c rear wheel to have a narrower road rear hub (130mm OLN) than a wider MTB hub (135mm OLN).
I wouldn't advise trying to fit them on a MTB.