Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. The capital and most populous city is Algiers, located in the far north of the country on the Mediterranean coast. With an area of 2,381,741 square kilometres (919,595 sq mi), Algeria is the tenth-largest country in the world, and the largest by area in the African Union and the Arab world. With an estimated population of over 43 million, it is the eighth-most populous country in Africa. Algeria is bordered to the northeast by Tunisia, to the east by Libya, to the southeast by Niger, to the southwest by Mali, Mauritania, and the Western Saharan territory, to the west by Morocco, and to the north by the Mediterranean Sea. It is a semi-presidential republic consisting of 48 provinces and 1,541 communes (counties). Pre-1962 Algeria has known many empires and dynasties, including ancient Numidians, Phoenicians, Carthaginians, Romans, Vandals, Byzantines, Umayyads, Abbasids, Idrisid, Aghlabid, Rustamid, Fatimids, Zirid, Hammadids, Almoravids, Almohads, Zayyanids, Spaniards, Ottomans and finally, the French colonial empire. Algeria is a regional and middle power. It has the highest human development index of all non-island African countries and one of the largest economies on the continent, based largely on energy exports.