Lucky & unlucky numbers

八 (bā, eight) is the most prized number in Chinese culture because it sounds like 发 (fā, 'to prosper/get rich') — phone numbers, car plates, floor numbers, wedding dates, and prices are all chosen to include it, sometimes at a real price premium. The 2008 Beijing Olympics deliberately opened at 8:08pm on 8/8/08.

四 (sì, four) is the opposite — it sounds like 死 (sǐ, 'death'), so many buildings skip a labeled 4th floor (jumping to '3A' or '5'), apartment units with a 4 are often discounted, and gifts are never given in sets of four. 六 (liù, six) is auspicious for smoothness, captured in the phrase 六六大顺 ('may everything go smoothly'), and 九 (jiǔ, nine) sounds like 久 (jiǔ, 'long-lasting'), making it a favorite for weddings and long-term wishes.

二百五 (èr bǎi wǔ, '250') is a special case worth knowing: as a stand-alone insult it means roughly 'idiot' or 'fool,' rooted in old slang about currency — so using 250 casually as a price or quantity without meaning to insult anyone can land as an unintended joke or minor offense, and locals will often laugh or wince at a bill or count that lands on exactly that number.