Asia is the world's largest and most populous continent. It covers 8.6 % of the Earth's total surface area (or 29.4 % ot its land area) and, with almost 4 billion people, it contains more than 60 % of the world's current human population. In Asia there are more than fifty states and dependencies. The highest point in Asia is Mount Everest (8,848 m) and the longest river is Yangtze Kiang (6,300 km).