69

69 = 3 x 23.

69 = 9 + 10 + 11 + 12 + 13 + 14.

69 is the only number whose square and cube together use all the digits from 0 to 9: 69² = 4761 and 69³ = 328509.

69 is the fifth number that stays the same when written upside down.

69 Hesperia is an asteroid discovered in 1861 by Italian astronomer Giovanni Schiaparelli.

Source: Phillips, R. 1994 Numbers: Facts, Figures and Fiction. Cambridge University Press.