Listing methods to prove that two rings are not isomorphic

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Really, this question comes down to listing propeties that are preserved by ring isomorphisms. Off the top of my head, I can think of:

  • cardinality of the ring
  • commutativity
  • the order of elements
  • being a UFD, PID, field etc.

What else is there?

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  • Having a multiplicative identity (!)
  • Being free, algebraically closed, real closed, Noetherian, Artinian, local, or (semi)simple
  • Its characteristic, dimension (over the prime field, Krull, projective, injective, global), depth, transcendence degree (when applicable)
  • Having isomorphic $R-Mod$s

Pretty much anything one can think of, in particular literally anything first-order expressible ("Isomorphic structures are a fortiori elementarily equivalent")