Somalia, officially the Federal Republic of Somalia, is the easternmost country in continental Africa. Stretching across the Horn of Africa, it borders Ethiopia to the west, Djibouti to the northwest, Kenya to the southwest, the Gulf of Aden to the north, and the Indian Ocean to the east. Somalia has the longest coastline on Africa's mainland. Somalia has an estimated population of 18.1 million, of which 2.7 million live in the capital and largest city, Mogadishu. One of Africa's most ethnically homogenous countries, around 85% of Somalia's residents are ethnic Somalis. The official languages of the country are Somali and Arabic, though Somali is the primary language. Somalia has historic and religious ties to the Arab world. The people are Muslims, adherents of the Sunni branch.