18985661 has 4 divisors (see below), whose sum is σ = 19427232. Its totient is φ = 18544092.

The previous prime is 18985657. The next prime is 18985667. The reversal of 18985661 is 16658981.

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 18985661 - 2² = 18985657 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18985667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 220721 + ... + 220806.

It is an arithmetic number, because the mean of its divisors is an integer number (4856808).

Almost surely, 2^18985661 is an apocalyptic number.

It is an amenable number.

18985661 is a deficient number, since it is larger than the sum of its proper divisors (441571).

18985661 is an equidigital number, since it uses as much as digits as its factorization.

18985661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 441570.

The product of its digits is 103680, while the sum is 44.

The square root of 18985661 is about 4357.2538369941. The cubic root of 18985661 is about 266.7730212922.

The spelling of 18985661 in words is "eighteen million, nine hundred eighty-five thousand, six hundred sixty-one".