781

781 = 11 x 71.

781 is a divisor of 5⁵ - 1.

781 is 11111 in base 5.

781 is a centered decagonal number.

781 is the maximum number of regions into which 39 lines divide the plane.

The oldest recorded eruption of Mt. Fuji in Japan occurred in the year 781.

Source: Positive Integers