18516681 has 10 divisors (see below), whose sum is σ = 27660842. Its totient is φ = 12344400.

The previous prime is 18516647. The next prime is 18516713. The reversal of 18516681 is 18661581.

It can be written as a sum of positive squares in only one way, i.e., 18352656 + 164025 = 4284^2 + 405^2 .

It is not a de Polignac number, because 18516681 - 2¹⁰ = 18515657 is a prime.

It is a super-2 number, since 2×18516681² = 685734950511522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18516781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 114220 + ... + 114381.

Almost surely, 2^18516681 is an apocalyptic number.

It is an amenable number.

18516681 is a deficient number, since it is larger than the sum of its proper divisors (9144161).

18516681 is an equidigital number, since it uses as much as digits as its factorization.

18516681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 228613 (or 228604 counting only the distinct ones).

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

The square root of 18516681 is about 4303.1013234643. The cubic root of 18516681 is about 264.5580910688.

The spelling of 18516681 in words is "eighteen million, five hundred sixteen thousand, six hundred eighty-one".