Let
be a ring with the set of nilpotents
. We prove that the following are equivalent:
(i)
is additively closed,
(ii)
is multiplicatively closed and
satisfies K\”othe’s conjecture,
(iii)
is closed under the operation
,
(iv)
is a subring of
.
Some applications and examples of rings with this property are given, with
an emphasis on certain classes of exchange and clean rings.



