Skepticblog has a good summary of the various superstitions about numbers that exist in Chinese culture. These superstitions all stem from the fact that homophones are so ubiquitous in Chinese. The article uses Cantonese for its examples, but on the whole they work equally well in Mandarin.
The classic instance is with the number 4, which is 四 (sì) in Chinese. This sounds very similar to the character 死 (sǐ), which means “death”. This leads to the number 4 being very undesirable for Chinese-speaking people. In some ways this isn’t even superstitious numerology - when “4th Street” sounds pretty much the same as “Death Street”, it’s just aesthetically unpleasant.
There is some of the usual silliness about how the language works: “Each word in the language has a monotonic sound and is represented in writing by a single character.” This is only really true in Literary Chinese . In the modern language, function words are nearly always two characters, sometimes more.
Despite that, it’s certainly well-worth reading. Most students of Chinese are aware of the famous 四 and 五 double-meanings, but there’s a lot of detail on all the digits and how they combine, plus some other random homophones.