According to the information in the postal code database, the postal code of Yunyang County in Chongqing is 404500. The first two digits of 40 represent provinces, municipalities and autonomous regions, the third digit 4 represents postal areas, the fourth digit 5 represents cities or counties, and the last two digits 00 represent specific delivery areas, such as the postal code of Yunyang Town, Yunyang County, Chongqing: 40450 1.