18804721 has 8 divisors (see below), whose sum is σ = 20480040. Its totient is φ = 17162112.

The previous prime is 18804719. The next prime is 18804739. The reversal of 18804721 is 12740881.

It can be written as a sum of positive squares in 4 ways, for example, as 314721 + 18490000 = 561^2 + 4300^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18804721 - 2¹ = 18804719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18804761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6970 + ... + 9283.

It is an arithmetic number, because the mean of its divisors is an integer number (2560005).

Almost surely, 2^18804721 is an apocalyptic number.

It is an amenable number.

18804721 is a deficient number, since it is larger than the sum of its proper divisors (1675319).

18804721 is a wasteful number, since it uses less digits than its factorization.

18804721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16355.

The product of its (nonzero) digits is 3584, while the sum is 31.

The square root of 18804721 is about 4336.4410522916. The cubic root of 18804721 is about 265.9228345712.

The spelling of 18804721 in words is "eighteen million, eight hundred four thousand, seven hundred twenty-one".