  We have carried out a study of superheavy nuclei in the framework of the
Relativistic Mean-Field theory. Relativistic Hartree-Bogoliubov (RHB)
calculations have been performed for nuclei with large proton and neutron
numbers. A finite-range pairing force of Gogny type has been used in the RHB
calculations. The ground-state properties of very heavy nuclei with atomic
numbers Z=100-114 and neutron numbers N=154-190 have been obtained. The results
show that in addition to N=184 the neutron numbers N=160 and N=166 exhibit an
extra stability as compared to their neighbors. For the case of protons the
atomic number Z=106 is shown to demonstrate a closed-shell behavior in the
region of well deformed nuclei about N=160. The proton number Z=114 also
indicates a shell closure. Indications for a doubly magic character at Z=106
and N=160 are observed. Implications of shell closures on a possible synthesis
of superheavy nuclei are discussed.
