Mongolia dwarfs Russia: about 1,560,428 km² km² against 16,879,701 km² km². At true size Mongolia is about 10.8× larger — the whole of Russia fits into Mongolia roughly 10 times.
Mongolia sits in Asia, Russia in Europe. On the old Mercator map the latitude gap distorted how large each felt beside the other; at true size the answer is simply 10.8×.
The old map muddied it further: Mercator inflates Mongolia about 2.2× and Russia about 6.1×, so on a Mercator-style map this pair appears 30.5× apart instead of the true 10.8×.
Mongolia fits 10× into Russia.