Egypt is one of the most populous countries in Africa and the Middle East. The majority of its estimated 71 million people live near the banks of the Nile River, in an area of about 40,000 sq km (15,000 sq mi), where the only arable land is found. The large areas of the Sahara Desert are sparsely inhabited. About half of Egypt's residents live in urban areas, with most spread across the densely populated centres of greater Cairo, Alexandria, Khartoum and other major cities in the Nile Delta.