18189918 has 48 divisors (see below), whose sum is σ = 41951520. Its totient is φ = 5683392.

The previous prime is 18189917. The next prime is 18189923. The reversal of 18189918 is 81998181.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18189917) 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 23 ways as a sum of consecutive naturals, for example, 21528 + ... + 22356.

It is an arithmetic number, because the mean of its divisors is an integer number (873990).

Almost surely, 2^18189918 is an apocalyptic number.

18189918 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 18189918, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (20975760).

18189918 is an abundant number, since it is smaller than the sum of its proper divisors (23761602).

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

18189918 is a wasteful number, since it uses less digits than its factorization.

18189918 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 913 (or 910 counting only the distinct ones).

The product of its digits is 41472, while the sum is 45.

The square root of 18189918 is about 4264.9640092268. The cubic root of 18189918 is about 262.9926313674.

The spelling of 18189918 in words is "eighteen million, one hundred eighty-nine thousand, nine hundred eighteen".