18804564721 has 4 divisors (see below), whose sum is σ = 19062161572. Its totient is φ = 18546967872.

The previous prime is 18804564719. The next prime is 18804564731. The reversal of 18804564721 is 12746540881.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12746540881 = 41 ⋅310891241.

It can be written as a sum of positive squares in 2 ways, for example, as 5422702321 + 13381862400 = 73639^2 + 115680^2 .

It is a cyclic number.

It is not a de Polignac number, because 18804564721 - 2¹ = 18804564719 is a prime.

It is a super-2 number, since 2×18804564721² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18804564731) 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 3 ways as a sum of consecutive naturals, for example, 128798316 + ... + 128798461.

It is an arithmetic number, because the mean of its divisors is an integer number (4765540393).

Almost surely, 2^18804564721 is an apocalyptic number.

It is an amenable number.

18804564721 is a deficient number, since it is larger than the sum of its proper divisors (257596851).

18804564721 is an equidigital number, since it uses as much as digits as its factorization.

18804564721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 257596850.

The product of its (nonzero) digits is 430080, while the sum is 46.

The spelling of 18804564721 in words is "eighteen billion, eight hundred four million, five hundred sixty-four thousand, seven hundred twenty-one".