18865171821 has 4 divisors (see below), whose sum is σ = 25153562432. Its totient is φ = 12576781212.

The previous prime is 18865171817. The next prime is 18865171823. The reversal of 18865171821 is 12817156881.

It is a happy number.

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 not a de Polignac number, because 18865171821 - 2² = 18865171817 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 (18865171823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3144195301 + ... + 3144195306.

It is an arithmetic number, because the mean of its divisors is an integer number (6288390608).

Almost surely, 2^18865171821 is an apocalyptic number.

It is an amenable number.

18865171821 is a deficient number, since it is larger than the sum of its proper divisors (6288390611).

18865171821 is an equidigital number, since it uses as much as digits as its factorization.

18865171821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6288390610.

The product of its digits is 215040, while the sum is 48.

The spelling of 18865171821 in words is "eighteen billion, eight hundred sixty-five million, one hundred seventy-one thousand, eight hundred twenty-one".