• 78 can be written using four 4's:
78 is nontrivially palindromic in base 5, base 7 and base 12.
78 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.
78 is an esthetic number in base 6 and base 10, because in such bases its adjacent digits differ by 1.
It is a sphenic number, since it is the product of 3 distinct primes.
78 is an admirable number.
78 is a Gilda number.
78 is an idoneal number.
It is an alternating number because its digits alternate between odd and even.
It is a house number.
78 is an undulating number in base 5 and base 7.
78 is strictly pandigital in base 4.
It is a Curzon number.
78 is a nontrivial repdigit in base 12.
It is a plaindrome in base 8, base 10, base 12, base 14 and base 16.
It is a nialpdrome in base 3, base 6, base 9, base 11, base 12, base 13 and base 15.
It is a zygodrome in base 12.
It is a congruent number.
It is a panconsummate number.
78 is the 12-th triangular number.
78 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
78 is a wasteful number, since it uses less digits than its factorization.
78 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 18.
The square root of 78 is about 8.8317608663. The cubic root of 78 is about 4.2726586817.
Subtracting from 78 its product of digits (56), we obtain a palindrome (22).
Multiplying 78 by its reverse (87), we get a triangular number (6786 = T116).