It takes 500 trillion cells to form a human body. There are 24 hours in a day, that is, 1.440 minutes 86400 seconds, 365 days in a year, 8760 hours 525600 minutes 3 1.536000 seconds. China has a land area of 9.6 million square kilometers (9.6 million), and China is the most populous country in the world with 65,400 people. The longest river in China is the Yangtze River, with a total length of 6,397 kilometers. The largest lake in China is Qinghai Lake, with a circumference of 360 kilometers and an area of 4,500 square kilometers. The fastest train in China is the Shanghai Maglev train, with a speed of 430 (430) kilometers per hour, which is the highest in the world. 000 (179.968 million) square kilometers, the largest continent in the world is Asia, with an area of 4,400 (4,400) square kilometers, and the largest country in the world is Russia, with an area of17075870 (17075870) square kilometers, the highest in the world. The longest river in the world is the Nile with a length of 667 1(667 1) km, and the deepest lake in the world is Lake Baikal with a depth of 1, 741(174/) m.