18991028 has 18 divisors (see below), whose sum is σ = 38660706. Its totient is φ = 8138928.

The previous prime is 18991019. The next prime is 18991033. The reversal of 18991028 is 82019981.

It can be written as a sum of positive squares in only one way, i.e., 15038884 + 3952144 = 3878^2 + 1988^2 .

It is a junction number, because it is equal to n+sod(n) for n = 18990982 and 18991000.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 48251 + ... + 48642.

It is an arithmetic number, because the mean of its divisors is an integer number (2147817).

Almost surely, 2^18991028 is an apocalyptic number.

It is an amenable number.

18991028 is an abundant number, since it is smaller than the sum of its proper divisors (19669678).

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

18991028 is a wasteful number, since it uses less digits than its factorization.

18991028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96911 (or 96902 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 38.

The square root of 18991028 is about 4357.8696630349. The cubic root of 18991028 is about 266.7981566810.

The spelling of 18991028 in words is "eighteen million, nine hundred ninety-one thousand, twenty-eight".