78

the dimension of the exceptional Lie group E₆ and several related objects.

a sphenic number, having 3 distinct prime factors.

an abundant number with an aliquot sum of 90.

a semiperfect number, as a multiple of a perfect number.

the 12th triangular number.

a palindromic number in bases 5 (303₅), 7 (141₇), 12 (66₁₂), 25 (33₂₅), and 38 (22₃₈).

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.

https://freeglobaluniversity.blogspot.com/search/label/Excel

https://8sib.blogspot.com/search/label/78