What is this nut called and can it be removed and reused/replaced?
I wish comments would allow pictures, but what you have is something generically called a &quot;push on fastener&quot;   I have to disagree with jsotola, I consider them &quot;barely reusable&quot;, they often break when when removing, esp. if old.   I wouldn't count on being able to re-use it.
I attached a pic of something what I think is close to what you have.