18321857921 has 4 divisors (see below), whose sum is σ = 18334417200. Its totient is φ = 18309298644.

The previous prime is 18321857881. The next prime is 18321857929. The reversal of 18321857921 is 12975812381.

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 18321857921 - 2¹⁰ = 18321856897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18321857929) 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, 6277451 + ... + 6280368.

It is an arithmetic number, because the mean of its divisors is an integer number (4583604300).

Almost surely, 2^18321857921 is an apocalyptic number.

It is an amenable number.

18321857921 is a deficient number, since it is larger than the sum of its proper divisors (12559279).

18321857921 is a wasteful number, since it uses less digits than its factorization.

18321857921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12559278.

The product of its digits is 241920, while the sum is 47.

The spelling of 18321857921 in words is "eighteen billion, three hundred twenty-one million, eight hundred fifty-seven thousand, nine hundred twenty-one".