The number 4 is considered particularly unlucky. This is mainly because of the sound of the word, which is very similar to the word for 'death'. Just as many westerners fear the number 13 and avoid it, some Chinese people try to avoid the number 4. For example, some hotels don't have a room or floor with that number, and there was no fourth series for some mobile phone companies.

The number 5 can have either negative or positive associations depending on how it is used. Number 6, like 4, is sometimes disliked because of sound associations; it sounds like the word for 'fall' or 'drop'. However, it isn't as much feared as number 4. There can also be negative associations with 7 as it has associations with ghosts and spirits, though this is not always seen as a bad thing.

In general, even numbers are preferred to odd ones, although there are plenty of exceptions as you can see from the above.