18406623561 has 4 divisors (see below), whose sum is σ = 24542164752. Its totient is φ = 12271082372.

The previous prime is 18406623551. The next prime is 18406623623. The reversal of 18406623561 is 16532660481.

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 a cyclic number.

It is not a de Polignac number, because 18406623561 - 2²¹ = 18404526409 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18406623541) 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, 3067770591 + ... + 3067770596.

It is an arithmetic number, because the mean of its divisors is an integer number (6135541188).

Almost surely, 2^18406623561 is an apocalyptic number.

It is an amenable number.

18406623561 is a deficient number, since it is larger than the sum of its proper divisors (6135541191).

18406623561 is an equidigital number, since it uses as much as digits as its factorization.

18406623561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6135541190.

The product of its (nonzero) digits is 207360, while the sum is 42.

The spelling of 18406623561 in words is "eighteen billion, four hundred six million, six hundred twenty-three thousand, five hundred sixty-one".