78109920 has 432 divisors, whose sum is σ = 329395248. Its totient is φ = 17418240.

The previous prime is 78109903. The next prime is 78109921. The reversal of 78109920 is 2990187.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (432).

It is a super-2 number, since 2×78109920² = 12202319204812800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78109921) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1905100 + ... + 1905140.

It is an arithmetic number, because the mean of its divisors is an integer number (762489).

Almost surely, 2^78109920 is an apocalyptic number.

78109920 is a gapful number since it is divisible by the number (70) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 78109920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (164697624).

78109920 is an abundant number, since it is smaller than the sum of its proper divisors (251285328).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

78109920 is a wasteful number, since it uses less digits than its factorization.

78109920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85 (or 58 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 36.

The square root of 78109920 is about 8837.9816700421. The cubic root of 78109920 is about 427.4664793661.

The spelling of 78109920 in words is "seventy-eight million, one hundred nine thousand, nine hundred twenty".