In Japan, lucky number is 7 too and also 3 and 8 is considered as good omen. 8 in Chinese character (Kanji) looks like spreading wide toward the future, which is believed as a symbol of prosperity. There are different stories about why Japanese likes 3. One of the reasons is that 3 express new chapter next to 1.
On the other hand, unlucky number is 4 and 9. 4 express death and 9 express suffering from something.