  Assuming that the $P_c(4312)^+$ is a $I(J^P)=\frac12(\frac32^-)$ compact
pentaquark, we study the mass spectrum of its S-wave hidden-charm partner
states in a color-magnetic interaction model. Combining the information from
their decays obtained in a simple rearrangement scheme, one finds that the
quantum numbers of $P_c(4457)^+$, $ P_c(4440)^+$, and $P_c(4337)^+$ can be
assigned to be $I(J^P)=\frac12(\frac32^-)$, $\frac12(\frac12^-)$, and
$\frac12(\frac12^-)$, respectively, while both $P_{cs}(4338)^0$ and
$P_{cs}(4459)^0$ can be interpreted as $I(J^P)=0(\frac12^-)$ $udsc\bar{c}$
compact states. Based on the numerical results, we also find narrow pentaquarks
in $ssnc\bar{c}$ ($n=u,d$) and $sssc\bar{c}$ systems. The decay properties of
the studied pentaquarks and the searching channels for them can be tested in
future experiments.
