28; twenty eight
4am
「二八」 has another reading with different meanings.
February and August (months when business is generally at its slowest)
二十八日に予約を入れた。
I made a reservation for the twenty-eighth.
二十八歳で初めて海外に行った。
I went abroad for the first time at twenty-eight.
二十八名が試験に合格した。
Twenty-eight people passed the exam.