Centre of a matrix ring are $ \operatorname{diag}\{ a, a, ..., a \} $ with $ a\in Z(R) $
4280
A linear operator commuting with all such operators is a scalar multiple of the identity.
27821
A problem on rank of $A$ and $\operatorname{adj}(A)$
79650
Division Rings and Division Algebras
37971
Prove that the center of a group is a normal subgroup
7418
The Center of $\operatorname{GL}(n,k)$
19112
Ring $R= \mathbb Z_3[x]/\langle x^6-1\rangle$
138410
Centralizer of $\mathbb{C}[G]$ in $\mathbb{C}[H]$
3778
If the matrix rings over two Rings of the same size are isomorphic, then the scalar rings are isomorphic
83483
Is there a nice way to classify the ideals of the ring of lower triangular matrices?
118781
product of ideals in matrix ring
12502
The center of a non-Abelian group of order 8
133482
$AB-BA$ is a nilpotent matrix if it commutes with $A$
11393
The center of the dihedral group
114320
Showing that if the center of a group is trivial, then the center of its automorphism group is trivial
97999
Explain these ring isomorphisms
46843
A ring without the Invariant Basis Number property
78298
On the nilpotence of the matrix $AB-BA$