18518516661 has 4 divisors (see below), whose sum is σ = 24691355552. Its totient is φ = 12345677772.

The previous prime is 18518516659. The next prime is 18518516711. The reversal of 18518516661 is 16661581581.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 18518516661 - 2¹ = 18518516659 is a prime.

It is a super-3 number, since 3×18518516661³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18518516661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18518516641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3086419441 + ... + 3086419446.

It is an arithmetic number, because the mean of its divisors is an integer number (6172838888).

Almost surely, 2^18518516661 is an apocalyptic number.

It is an amenable number.

18518516661 is a deficient number, since it is larger than the sum of its proper divisors (6172838891).

18518516661 is an equidigital number, since it uses as much as digits as its factorization.

18518516661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6172838890.

The product of its digits is 345600, while the sum is 48.

The spelling of 18518516661 in words is "eighteen billion, five hundred eighteen million, five hundred sixteen thousand, six hundred sixty-one".