18556681561 has 8 divisors (see below), whose sum is σ = 20896674048. Its totient is φ = 16325526000.

The previous prime is 18556681547. The next prime is 18556681601. The reversal of 18556681561 is 16518665581.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18556681561 - 2⁵ = 18556681529 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 18556681499 and 18556681508.

It is not an unprimeable number, because it can be changed into a prime (18556684561) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27208870 + ... + 27209551.

It is an arithmetic number, because the mean of its divisors is an integer number (2612084256).

Almost surely, 2^18556681561 is an apocalyptic number.

18556681561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18556681561 is a deficient number, since it is larger than the sum of its proper divisors (2339992487).

18556681561 is a wasteful number, since it uses less digits than its factorization.

18556681561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54418463.

The product of its digits is 1728000, while the sum is 52.

The spelling of 18556681561 in words is "eighteen billion, five hundred fifty-six million, six hundred eighty-one thousand, five hundred sixty-one".