And (n ≥ 1) = 48
(Nakute nanakuse; “None, seven quirks”)
Even someone who appears completely normal has their quirks, flaws, or questionable habits. Nobody is truly ordinary or above criticism. Everybody has their own faults.
This compact idiom depends on elision. It begins with the adjective 無い (nai), “not,” in conjunctive form, followed by the number-noun 七癖 (nana-kuse), “seven habits.” (The implication is that the “habits” would be considered odd or bad, although examples such as verbal tics also fall into this category.)
Grammatically, this phrase simply doesn’t work as it stands; it should be read not literally but as shorthand for something along the lines of “(Even if it appears that somebody has) none, (they actually have) seven (hidden) quirks.”
It’s said that the reason “seven” was chosen was simple alliteration: the nas in nana match up with the na in nai. Accordingly, while reading 七 as shichi is not strictly an error, it should probably be avoided.
Some versions of this expressions follow with あって四十八癖 (atte shijuuhakkuse), e.g. “Someone who has visible quirks then will have forty-eight of them.” – This number chosen due to 48 traditionally indicating a comprehensive set, as in the 48 basic techniques of sumo.
(“Nakute nanakuse de, mattaku motte ippanjin da to omotta ani de mo, kushami no ato, ‘Guaa’ to ka hen na koe wo dasu kuse ga aru no ni saikin ki ga tsuita nda.”)
[“It’s said that everybody has their quirks – recently I noticed that even my older brother, who I’d thought was perfectly ordinary, has this habit of making weird noises like ‘Guh’ after sneezing.”]