18909021 has 4 divisors (see below), whose sum is σ = 25212032. Its totient is φ = 12606012.

The previous prime is 18909019. The next prime is 18909041. The reversal of 18909021 is 12090981.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 18909021 - 2¹ = 18909019 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18909021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18909041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3151501 + ... + 3151506.

It is an arithmetic number, because the mean of its divisors is an integer number (6303008).

Almost surely, 2^18909021 is an apocalyptic number.

It is an amenable number.

18909021 is a deficient number, since it is larger than the sum of its proper divisors (6303011).

18909021 is an equidigital number, since it uses as much as digits as its factorization.

18909021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6303010.

The product of its (nonzero) digits is 1296, while the sum is 30.

The square root of 18909021 is about 4348.4504136531. The cubic root of 18909021 is about 266.4135735809.

The spelling of 18909021 in words is "eighteen million, nine hundred nine thousand, twenty-one".