Egypt is one of the most populous countries in Africa and the Middle East, and the 15th most populated in the world. The great majority of its over 82 million people live near the banks of the Nile River, an area of about 40,000 sq km (15,000 sq mi), where the only arable land is found. The large regions of the Sahara Desert, which constitute most of Egypt's territory, 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 and other major cities in the Nile Delta.