What is the coordination number of cobalt in [Co(NH3)6]Cl3?

The number of atoms of the ligands that are directly bound to the central metal atom or ion by the coordinate bond is known as the coordination number of the metal atom or ion. Co is surrounded by 6 ammonia compounds and is directly bound to the metal. Hence, the coordination number of the given compound will be 6. Therefore, the correct option is (c).