18662605561 has 4 divisors (see below), whose sum is σ = 18686319952. Its totient is φ = 18638891172.

The previous prime is 18662605553. The next prime is 18662605583. The reversal of 18662605561 is 16550626681.

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, and also an emirpimes, since its reverse is a distinct semiprime: 16550626681 = 163 ⋅101537587.

It is a cyclic number.

It is not a de Polignac number, because 18662605561 - 2³ = 18662605553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18662605501) 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, 11856015 + ... + 11857588.

It is an arithmetic number, because the mean of its divisors is an integer number (4671579988).

Almost surely, 2^18662605561 is an apocalyptic number.

It is an amenable number.

18662605561 is a deficient number, since it is larger than the sum of its proper divisors (23714391).

18662605561 is an equidigital number, since it uses as much as digits as its factorization.

18662605561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23714390.

The product of its (nonzero) digits is 518400, while the sum is 46.

The spelling of 18662605561 in words is "eighteen billion, six hundred sixty-two million, six hundred five thousand, five hundred sixty-one".