Various names have been given to the Indus River, from the Persian words "Mehram" and "Sindhu" to the Greek "Greek word for Indus River taken from the old Persian word "Hindus". It is one of the largest rivers in the world, with a total drainage area of over 1.1 million km2 (more than a quarter of the Earth's surface). The Indus River is named after the ancient Indian civilization of the same name, which flourished along its banks. The Indus River was a crucial factor in the development of the Indus Valley Civilization.