(78, LXXVIII) is the natural number
and followed by seventy-nine
. It is a triangular number
as well as a composite number
, with its divisors being 1, 2, 3, 6, 13, 26, 39 and 78, and its factorization
makes it a sphenic number.
Karl A. Dahlke proved in 1989 that 78 heptominoss of this shape ( ), at a minimum, must be used in order to fill a rectangle.
78 is also:
See also: seventy
- For the year A.D. 78, see 78.