In Japan, 9 is unlucky, probably because it sounds similar to the Japanese word for “suffering”.
In Italy, it’s 17. In China, 4 sounds like “death” and is more actively avoided in everyday life than 13 is in Western culture – including a willingness to pay higher fees to avoid it in cellphone numbers.
And though 666 is considered lucky in China, many Christians around the world associate it with an evil beast described in the biblical Book of Revelation. There is even a word for an intense fear of 666: Hexakosioihexekontahexaphobia.
SOCIAL AND PSYCHOLOGICAL EXPLANATIONS
There are many kinds of specific phobias, and people hold them for a variety of psychological reasons. They can arise from direct negative experiences – fearing bees after being stung by one, for example. Other risk factors for developing a phobia include being very young, having relatives with phobias, having a more sensitive personality and being exposed to others with phobias.
Part of 13’s reputation may be connected to a feeling of unfamiliarity, or “felt sense of anomaly”, as it is called in the psychological literature.
In everyday life, 13 is less common than 12. There’s no 13th month, 13-inch ruler, or 13 o’clock. By itself a sense of unfamiliarity won’t cause a phobia, but psychological research shows that we favour what is familiar and disfavour what is not. This makes it easier to associate 13 with negative attributes.
People also may assign dark attributes to 13 for the same reason that many believe in “full moon effects”. Beliefs that the full moon influences mental health, crime rates, accidents and other human calamities have been thoroughly debunked. Still, when people are looking to confirm their beliefs, they are prone to infer connections between unrelated factors.
For example, having a car accident during a full moon, or on a Friday the 13th, makes the event seem all the more memorable and significant. Once locked in, such beliefs are very hard to shake.
Source By https://www.channelnewsasia.com/commentary/superstition-lucky-bad-luck-friday-13-social-psychology-3030676