18999990 has 48 divisors (see below), whose sum is σ = 49886928. Its totient is φ = 5016768.

The previous prime is 18999989. The next prime is 18999991. The reversal of 18999990 is 9999981.

18999990 is nontrivially palindromic in base 12.

It is an interprime number because it is at equal distance from previous prime (18999989) and next prime (18999991).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18999991) 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, 8644 + ... + 10616.

It is an arithmetic number, because the mean of its divisors is an integer number (1039311).

Almost surely, 2^18999990 is an apocalyptic number.

18999990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 18999990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24943464).

18999990 is an abundant number, since it is smaller than the sum of its proper divisors (30886938).

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

18999990 is a wasteful number, since it uses less digits than its factorization.

18999990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2093 (or 2090 counting only the distinct ones).

The product of its (nonzero) digits is 472392, while the sum is 54.

The square root of 18999990 is about 4358.8977964619. The cubic root of 18999990 is about 266.8401180581.

Subtracting from 18999990 its reverse (9999981), we obtain a palindrome (9000009).

The spelling of 18999990 in words is "eighteen million, nine hundred ninety-nine thousand, nine hundred ninety".