The number nine is special in China as it is seen as number of the heaven, and Chinese dragons are frequently connected with it.
The physical attributes of a Chinese dragon are very precise.
Normally described in terms of nine attributes and usually has 117 (9x13) scales - 81 (9x9) Yang and 36 (9x4) Yin.
This is also why there are nine forms of the dragon and there are 9 sons of the dragon
The Nine-Dragon Wall is a spirit wall with images of nine different dragons, and is found in imperial Chinese palaces and gardens.
As nine was considered the number of the emperor, only the most senior officials were allowed to wear nine dragons on their robes — and then only with the robe completely covered with surcoats.
Lower-ranking officials had eight or five dragons on their robes, again covered with surcoats; even the emperor himself wore his dragon robe with one of its nine dragons hidden from view.
There are a number of places in China called "Nine Dragons", the most famous being Kowloon (in Cantonese) in Hong Kong.
The part of the Mekong in Vietnam is known as Cửu Long, with the same meaning.