The number four (4) is a very unlucky number because the pronounciation for it sounds very similar to 'death.' In fact, in pinyin, they have the same lettering. Four is 'si' and death is also...
Yes some cultures do have unlucky numbers. French is 9 America,England,Australia and some more is 13 Russia is 6 German is 4 China is 8 New Zealand is 3 I'm pretty sure theres more but i dont know...