18646664681 has 4 divisors (see below), whose sum is σ = 18665368452. Its totient is φ = 18627960912.

The previous prime is 18646664599. The next prime is 18646664689.

18646664681 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6160837081 + 12485827600 = 78491^2 + 111740^2 .

It is a cyclic number.

It is not a de Polignac number, because 18646664681 - 2²² = 18642470377 is a prime.

It is a super-4 number, since 4×18646664681⁴ (a number of 42 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18646664689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9350390 + ... + 9352383.

It is an arithmetic number, because the mean of its divisors is an integer number (4666342113).

Almost surely, 2^18646664681 is an apocalyptic number.

It is an amenable number.

18646664681 is a deficient number, since it is larger than the sum of its proper divisors (18703771).

18646664681 is an equidigital number, since it uses as much as digits as its factorization.

18646664681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18703770.

The product of its digits is 7962624, while the sum is 56.

The spelling of 18646664681 in words is "eighteen billion, six hundred forty-six million, six hundred sixty-four thousand, six hundred eighty-one".