Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 482,286.55 km2 (182,812 mi.2), including adjacent islands such as Simeulue, Nias, the Mentawai Islands, Enggano, the various achipelagoes comprising the Riau Islands Province, Bangka and Belitung and the Krakatoa archipelago.