Uzbek are a Turkic ethnic group in Central Asia, mainly found in Uzbekistan. They are also found in large numbers in Afghanistan, Tajikstan, Kyrgyzstan, Turkmenistan, Kazakhstan, Russia, Pakistan, Mongolia and China. The ancestors of the Uzbeks were various Altaic-speaking tribes and Iranians living in Central Asia. In the 13th century Mongols, led by Genghis Khan, invaded Central Asia and absorbed many ethnic groups of the region into it. The term Uzbek came after the name of a converted Muslim Khan Uzbeg (1282–1341, reign 1313–1341), the longest-reigning khan of the Golden Horde of the Mongol Empire. All subjects of his khanate were known as Uzbeks. In general, Uzbeks were converted to Islam as early as the 8th century when Arab troops entered Central Asia. Uzbek in China is a Muslim ethnic group. Their forefathers were the Central Asian Uzbek who, along the Silk Road, came to China for trading. Some of them settled in China and gradually formed Chinese Uzbek. Today, they mainly live in Xinjiang, notably Yining, Tacheng, Kashgar, Shache, Yecheng and Urumqi. The estimated number is below 20,000 (12,370 according to census 2000) in the northwestern province of China. Uzbeks speak Uzbeki Language, a Altaic branch of Turkic Language family, using primarily Arabic characters.