Algeria (Arabic: الجزائر al-Jazā'ir; Berber: Dzayer), officially People's Democratic Republic of Algeria, is a country in North Africa on the Mediterranean coast. Its capital and most populous city is Algiers. 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 in Africa and the Arab world. Algeria is bordered to the northeast by Tunisia, to the east by Libya, to the west by Morocco, to the southwest by Western Sahara, Mauritania, and Mali, to the southeast by Niger, and to the north by the Mediterranean Sea. The country is a semi-presidential republic consisting of 48 provinces and 1,541 communes. Abdelaziz Bouteflika has been President since 1999.Ancient 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, Ottomans and the French colonial empire. Berbers are generally considered to be the indigenous inhabitants of Algeria. Following the Arab conquest of North Africa, most indigenous inhabitants were Arabised; thus, although most Algerians are Berber in origin, most identify with Arab culture. En masse, Algerians are a mix of Berbers, Arabs, Turks and Black Africans.The North African country supplies large amounts of natural gas to Europe, and energy exports are the backbone of the economy. According to OPEC Algeria has the 17th largest oil reserves in the world and the second largest in Africa, while it has the 9th largest reserves of natural gas. Sonatrach, the national oil company, is the largest company in Africa. Algeria has one of the largest militaries in Africa and the largest defence budget on the continent; most of Algeria's weapons are imported from Russia, with whom they are a close ally. Algeria is a member of the African Union, the Arab League, OPEC, the United Nations and is the founding member of the Maghreb Union.