Special meanings applied to numbers 0 - 10
There is a Wikipedia article dedicated to this, Numbers in Chinese culture; it states that numbers are divided in two categories, lucky and unlucky numbers.

Lucky Numbers:


二, the number 2: There is a saying that states "Good things come in pairs", for this reason many things in China seem to be "presented" in pairs of two, since this is considered a positive number;
三, the number 3: It's considered lucky because it's similar to the character for "birth", 生.
五, the number 5: This number is associated with the Five Elements (Earth, Water, Wind, Fire and Metal) and also with the Emperor of China; the Tianamen Gate has five arches;
六, the number 6: The number six pronounced as liù, is similar to the character 流 (liú) which means "to flow". This is considered lucky in business. Side-note: I've read elsewhere that objects with this number or with the string with three 6 in a row are considered very lucky, and people will try to buy such things (such as phone numbers). It's stated in this page, "Deciphering The Meaning Of Chinese Numbers";
七, the number 7: It's a lucky number for relationships.
八, the number 8: It sounds similar to the word for "prosper" or "wealth" 發 (fā), short for "發財". 
九, the number 9: This number, like 五, was historically associated with the Emperor of China. As it's stated in that article, "before the establishment of the imperial examinations officials were organized in the nine-rank system, the nine bestowments were rewards the Emperor made for officials of extraordinary capacity and loyalty, while the nine familial exterminations was one of the harshest punishments the Emperor sentenced; the Emperor's robes often had nine dragons, and Chinese mythology held that the dragon has nine children."


Unlucky Numbers:


四, the number 4: As you said, this number is associated with death, 死 (sǐ). This happens in Japanese as well, by the way, both 四 and 死, can be read as "shi". Following the same logic for the number 6, objects/things with this number are avoided, such as floors... A similar attitude in westerner countries which miss the 13th floor, for example.


Some numbers that were considered as lucky, can be considered unlucky too:


五, the number 5: It's also associated to the character 無 (wú) "not". If associated with something bad, it can become positive, such as in the number 54, because it means "not + death". 528, instead might mean "no easy fortune for me".
六, the number 6: "Six in Cantonese which has a similar pronunciation to that of "lok6" (落, meaning, to drop, fall, or decline)"
七, the number 7: As stated in the article this number "is considered spiritist or ghostly". However, since the 7th day of the month, in the Chinese lunar calendar, is Valentine's Day, this number is not usually associated with bad luck.


I tried to summarize most of the content here, but check the page for more info and other meanings of complex numbers.