78 (number)
78 is the natural number following 77 and preceding 79.
In mathematics
78 is:- the 5th discrete tri-prime; or also termed Sphenic number, and the 4th of the form.
- an abundant number with an aliquot sum of 90; within an aliquot sequence of nine composite numbers to the Prime in the 3-aliquot tree.
- a semiperfect number, as a multiple of a perfect number.
- the 12th triangular number.
- a palindromic number in bases 5, 7, 12, 25, and 38.
- a Harshad number in bases 3, 4, 5, 6, 7, 13 and 14.
- an Erdős–Woods number, since it is possible to find sequences of 78 consecutive integers such that each inner member shares a factor with either the first or the last member.
- the dimension of the exceptional Lie group E6 and several related objects.
- the smallest number that can be expressed as the sum of four distinct nonzero squares in more than one way:, or .