Well, I don’t think that’s disputed anywhere seriously. Pretty much we and Russia are about equal, them 5500, us 5000. And between we two, that is about 88% of the world’s arsenal.
People do argue abut qualitative differences, but that’s about the state of things.
https://fas.org/initiative/status-world-nuclear-forces/
Russia’s Mayak plant, the one that makes and reprocesses nuclear cores, has been closed since 2017. Russian nukes have a short life of about ten years.
Add to this that their budget for maintaining a nuclear stockpile is woefully short of supporting 5,000+ devices and it’s not hard to conclude they’re far weaker than they let on.
I’d estimate they have 200-250 devices with a 90% expectancy of function and another 1,000 or so of various capabilities. The rest are useless.
This is still serious, but in no way are they the #1 nuclear power anymore. That ended three decades ago.