18861691 has 4 divisors (see below), whose sum is σ = 18896112. Its totient is φ = 18827272.

The previous prime is 18861683. The next prime is 18861707. The reversal of 18861691 is 19616881.

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

It is a cyclic number.

It is not a de Polignac number, because 18861691 - 2³ = 18861683 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18861191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16375 + ... + 17488.

It is an arithmetic number, because the mean of its divisors is an integer number (4724028).

Almost surely, 2^18861691 is an apocalyptic number.

18861691 is a deficient number, since it is larger than the sum of its proper divisors (34421).

18861691 is an equidigital number, since it uses as much as digits as its factorization.

18861691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34420.

The product of its digits is 20736, while the sum is 40.

The square root of 18861691 is about 4343.0048353646. The cubic root of 18861691 is about 266.1911067548.

The spelling of 18861691 in words is "eighteen million, eight hundred sixty-one thousand, six hundred ninety-one".