18810021 has 32 divisors (see below), whose sum is σ = 27498240. Its totient is φ = 11404800.

The previous prime is 18809993. The next prime is 18810073. The reversal of 18810021 is 12001881.

It is not a de Polignac number, because 18810021 - 2⁹ = 18809509 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 18810021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18810091) 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 31 ways as a sum of consecutive naturals, for example, 172515 + ... + 172623.

It is an arithmetic number, because the mean of its divisors is an integer number (859320).

Almost surely, 2^18810021 is an apocalyptic number.

It is an amenable number.

18810021 is a deficient number, since it is larger than the sum of its proper divisors (8688219).

18810021 is a wasteful number, since it uses less digits than its factorization.

18810021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 237.

The product of its (nonzero) digits is 128, while the sum is 21.

The square root of 18810021 is about 4337.0521094402. The cubic root of 18810021 is about 265.9478151534.

The spelling of 18810021 in words is "eighteen million, eight hundred ten thousand, twenty-one".