Nigeria, formally known as the Federal Republic of Nigeria, is a West African country. It lies in the Atlantic Ocean, between the Sahel to the north and the Gulf of Guinea to the south. It has an area of 923,769 square kilometers. With a population of over 230 million, it is Africa's most populated country and the world's sixth-largest. Nigeria borders Niger to the north, Chad to the northeast, Cameroon to the east, and Benin to the west. Nigeria is a federal republic with 36 states and the Federal Capital Territory, which includes the capital, Abuja. Lagos is Nigeria's largest metropolis, one of the world's largest metropolitan regions, and Africa's most significant. Nigeria's economy is the fourth-largest in Africa, the 53rd-largest globally by nominal GDP, and the 27th-largest by PPP. Nigeria is commonly called the Giant of Africa due to its massive population and economy, and the World Bank considers it an emerging market.