18991878 has 16 divisors (see below), whose sum is σ = 39010800. Its totient is φ = 6159456.

The previous prime is 18991867. The next prime is 18991879. The reversal of 18991878 is 87819981.

It is a self number, because there is not a number n which added to its sum of digits gives 18991878.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18991879) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 42553 + ... + 42996.

It is an arithmetic number, because the mean of its divisors is an integer number (2438175).

Almost surely, 2^18991878 is an apocalyptic number.

18991878 is an abundant number, since it is smaller than the sum of its proper divisors (20018922).

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

18991878 is a wasteful number, since it uses less digits than its factorization.

18991878 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85591.

The product of its digits is 290304, while the sum is 51.

The square root of 18991878 is about 4357.9671866594. The cubic root of 18991878 is about 266.8021370703.

The spelling of 18991878 in words is "eighteen million, nine hundred ninety-one thousand, eight hundred seventy-eight".