18521943891 has 32 divisors (see below), whose sum is σ = 27860336640. Its totient is φ = 10843677600.

The previous prime is 18521943859. The next prime is 18521943917. The reversal of 18521943891 is 19834912581.

It is not a de Polignac number, because 18521943891 - 2⁵ = 18521943859 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18521943191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 559870 + ... + 592028.

It is an arithmetic number, because the mean of its divisors is an integer number (870635520).

Almost surely, 2^18521943891 is an apocalyptic number.

18521943891 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

18521943891 is a deficient number, since it is larger than the sum of its proper divisors (9338392749).

18521943891 is a wasteful number, since it uses less digits than its factorization.

18521943891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32767.

The product of its digits is 622080, while the sum is 51.

The spelling of 18521943891 in words is "eighteen billion, five hundred twenty-one million, nine hundred forty-three thousand, eight hundred ninety-one".