  Very recently, the LHCb Collaboration reported a fully charmed tetraquark
state $X(6900)$ in the invariant mass spectrum of $J/\psi$ pairs. If one
$J/\psi$ meson is replaced with a fully charmed baryon, we obtain a fully
charmed pentaquark candidate. In this work, we perform a systematic study on
the mass spectra of the S-wave fully heavy pentaquark $QQQQ\bar{Q}$ in the
framework of the chromomagnetic interaction model. Based on our results in two
different schemes, we further investigate the decay behaviors for them. We hope
that our study will be helpful in searching for such types of exotic pentaquark
states in experiments in the future.
