18181566681 has 16 divisors (see below), whose sum is σ = 25044610560. Its totient is φ = 11720424960.

The previous prime is 18181566643. The next prime is 18181566703. The reversal of 18181566681 is 18666518181.

It is a happy number.

It is not a de Polignac number, because 18181566681 - 2⁷ = 18181566553 is a prime.

It is a super-2 number, since 2×18181566681² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18181562681) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 34761 + ... + 193833.

It is an arithmetic number, because the mean of its divisors is an integer number (1565288160).

Almost surely, 2^18181566681 is an apocalyptic number.

It is an amenable number.

18181566681 is a deficient number, since it is larger than the sum of its proper divisors (6863043879).

18181566681 is a wasteful number, since it uses less digits than its factorization.

18181566681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160336.

The product of its digits is 552960, while the sum is 51.

The spelling of 18181566681 in words is "eighteen billion, one hundred eighty-one million, five hundred sixty-six thousand, six hundred eighty-one".