18800021 has 4 divisors (see below), whose sum is σ = 18816000. Its totient is φ = 18784044.

The previous prime is 18800003. The next prime is 18800027. The reversal of 18800021 is 12000881.

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 a cyclic number.

It is not a de Polignac number, because 18800021 - 2¹⁸ = 18537877 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 18799966 and 18800002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18800027) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6071 + ... + 8628.

It is an arithmetic number, because the mean of its divisors is an integer number (4704000).

Almost surely, 2^18800021 is an apocalyptic number.

It is an amenable number.

18800021 is a deficient number, since it is larger than the sum of its proper divisors (15979).

18800021 is a wasteful number, since it uses less digits than its factorization.

18800021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15978.

The product of its (nonzero) digits is 128, while the sum is 20.

The square root of 18800021 is about 4335.8990993795. The cubic root of 18800021 is about 265.9006780524.

The spelling of 18800021 in words is "eighteen million, eight hundred thousand, twenty-one".