18385561 has 4 divisors (see below), whose sum is σ = 18637492. Its totient is φ = 18133632.

The previous prime is 18385547. The next prime is 18385607. The reversal of 18385561 is 16558381.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11095561 + 7290000 = 3331^2 + 2700^2 .

It is a cyclic number.

It is not a de Polignac number, because 18385561 - 2⁵ = 18385529 is a prime.

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 18385561.

It is not an unprimeable number, because it can be changed into a prime (18385361) 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, 125856 + ... + 126001.

It is an arithmetic number, because the mean of its divisors is an integer number (4659373).

Almost surely, 2^18385561 is an apocalyptic number.

It is an amenable number.

18385561 is a deficient number, since it is larger than the sum of its proper divisors (251931).

18385561 is an equidigital number, since it uses as much as digits as its factorization.

18385561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 251930.

The product of its digits is 28800, while the sum is 37.

The square root of 18385561 is about 4287.8387329749. The cubic root of 18385561 is about 263.9321498806.

The spelling of 18385561 in words is "eighteen million, three hundred eighty-five thousand, five hundred sixty-one".