In Chinese, 666 is a very good number. 6 sounds like the character 溜 which technically means something like smooth flowing but is used to compliment someone's

In Chinese, 666 is a very good number. 6 sounds like the character 溜 which technically means something like smooth flowing but is used to compliment someone's well-practiced skills. "666" is often said when someone does something impressive and smoothly. Like if someone double-flips a pancake and it lands perfectly, that's the kind of situation you'd say "666" to compliment them.