18165681 has 8 divisors (see below), whose sum is σ = 26912160. Its totient is φ = 12110436.

The previous prime is 18165647. The next prime is 18165683. The reversal of 18165681 is 18656181.

It is not a de Polignac number, because 18165681 - 2¹⁸ = 17903537 is a prime.

It is a super-2 number, since 2×18165681² = 659983932387522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (18165683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 336375 + ... + 336428.

It is an arithmetic number, because the mean of its divisors is an integer number (3364020).

Almost surely, 2^18165681 is an apocalyptic number.

It is an amenable number.

18165681 is a deficient number, since it is larger than the sum of its proper divisors (8746479).

18165681 is an equidigital number, since it uses as much as digits as its factorization.

18165681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 672812 (or 672806 counting only the distinct ones).

The product of its digits is 11520, while the sum is 36.

The square root of 18165681 is about 4262.1216547630. The cubic root of 18165681 is about 262.8757720251.

The spelling of 18165681 in words is "eighteen million, one hundred sixty-five thousand, six hundred eighty-one".