There's no 'M-factor'. Just multiply by 1.6x. The 22mm f/2 pancake gives the FoV of a 35mm lens on FF (35mm film), and the DoF of f/3.2 (if you frame the scene the same, and that's because you'd be further away with 22mm on the EOS M than 35mm on FF, and more distance means deeper DoF).
Is that correct, Neuro? You'd be further away with the M if you were using the same lens on both cameras, but in the above scenario won't both cameras be at the same distance?
True, I didn't phrase that very well…sorry. 22mm on FF vs APS-C, you're further away on APS-C so DoF is deeper. 22mm on APS-C vs. 35mm on FF, you're at the same distance, but the focal length is shorter on APS-C, so DoF is deeper.
Bottom line, the FF equivalent of the 22mm f/2 on APS-C (i.e. EOS M) is a hypothetical 35mm f/3.2 lens.