For a second, pretend we have GAT, Const Generics, and whatever your favorite type system feature is.
What numeric traits would make sense to have in std? What numeric traits would make sense to not have in std, but in a "2nd party" (i.e. officially endorced) crate? What numeric traits might be useful but can be relegated to a 3rd party crate?
I'm not really concerned with how the traits would be laid out. I'm interested in what functionality you think deserves to be standardized vocabulary for talking about types in programs.
numtraits is the current goto for numerical traits, of which I'll reproduce a few highlights below:

NumOps
: just an alias forAdd
+Sub
+Div
+Mul

Zero
/One
: additive and multiplicative identity 
Float
: operations that make sense on a floating point number 
Real
: mathematical real numbers without floating point oddities required 
PrimInt
: trivially copyable, two's compliment integers
I personally think that abstractions for higher level mathematical concepts (rings, graphs, etc) aren't generally applicable enough to live in std, but basic numerics feels simple and universal to potentially deserve a spot in std.