Russia's a big place. The European area would likely be wiped off the map, but I reckon the rest would remain largely intact - and ripe for invasion by countries left intact, but destitute and in need resources that they can no longer import.
For every nuke Russia launched, they'd get two back
It's not just the immediate effects either. The long term effects of radiation doesn't just affect humans. Animals, Land, Water Supplies and Air would be contaminated.
The natural movement of the air woudl spread the radioactivity all over the globe.
The effect of the blasts would also likely lead to a nuclear winter which would finish off all the remaining vegetation and animals. Smaller creatures like cockroaches and maybe rats and the like would probably survive and you'd have pockets of humanity that were lucky or in bunkers that might get away with it for a time and that's not even taking into account the holes being blasted into the ozone layer which would destroy the protection from the suns rays;
The researchers found that if the U.S. and Russia were each to launch their entire nuclear arsenals at one another, soot would drift high into the atmosphere, blotting out the sun for months to years. Summers would become a thing of the past, with temperatures throughout much of the Northern Hemisphere dipping below freezing year-round. Growing seasons would be cut by 90%, and most of the world would be plagued by famine.
In addition to dropping surface temperatures, nuclear winter would have a major impact on everything from ocean currents to the jet stream. The study's model predicted a seven-year-long El Niño, a normally yearlong weather pattern in the Pacific Ocean that usually occurs only every three to seven years. It leads to either drought or extreme rainfall in affected regions.
During a nuclear winter, people turning to the oceans to supplement dwindling crops would be disappointed, as much of the ocean's biodiversity would also disappear. Finally, as if the effects on climate weren't enough, soot would poke huge holes in the ozone layer, bombarding the surface of Earth with ultraviolet radiation.
This isn't the first time scientists have warned of the potentially disastrous climatic consequences of nuclear war. In the early 1980s, the height of the nuclear arms race, scientists (including astronomer Carl Sagan) first hypothesized that smoke from nuclear explosions could blot out the sun, drastically altering Earth's climate. The term "nuclear winter" was coined in 1983, when a landmark study in the journal Science calculated that temperatures could fall below freezing in the middle of continents.
https://www.livescience.com/nuclear-winter-disaster.html