Numbers / 78

The Number 78

78 is composite: factorization 2 × 3 × 13. That gives 78 exactly 8 divisors: 1, 2, 3, 6, 13, 26, 39, 78. 78's proper divisors total 90, 12 more than 78 itself, so 78 is abundant. 78 is also the 12th triangular number, the sum of 1 through 12. 78 has a digit sum of 15; for 78, the digital root works out to 6. 78: 2, 3, 6 all divide 78 evenly, out of 2-12. 78 is 1001110 in binary and 4E in hex; as a Roman numeral it's LXXVIII.