  In this paper, first, we define and investigate $k$-layered numbers, which
are a generalization of Zumkeller numbers. After that, we generalize the
concept of Zumkeller labeling and Zumkeller cordial labeling to $k$-layered
labeling and $k$-layered cordial labeling, respectively. Moreover, we prove
that every simple graph admits Zumkeller labeling, Zumkeller cordial labeling,
3-layered labeling, 3-layered cordial labeling, 4-layered labeling and
4-layered cordial labeling.
