18091998 has 40 divisors (see below), whose sum is σ = 41948280. Its totient is φ = 5821200.

The previous prime is 18091993. The next prime is 18092023. The reversal of 18091998 is 89919081.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18091991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 2773 + ... + 6623.

It is an arithmetic number, because the mean of its divisors is an integer number (1048707).

Almost surely, 2^18091998 is an apocalyptic number.

18091998 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 18091998, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (20974140).

18091998 is an abundant number, since it is smaller than the sum of its proper divisors (23856282).

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

18091998 is a wasteful number, since it uses less digits than its factorization.

18091998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3894 (or 3885 counting only the distinct ones).

The product of its (nonzero) digits is 46656, while the sum is 45.

The square root of 18091998 is about 4253.4689372323. The cubic root of 18091998 is about 262.5198678840.

The spelling of 18091998 in words is "eighteen million, ninety-one thousand, nine hundred ninety-eight".