18309011921 has 4 divisors (see below), whose sum is σ = 18348728244. Its totient is φ = 18269295600.

The previous prime is 18309011911. The next prime is 18309011923. The reversal of 18309011921 is 12911090381.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7810140625 + 10498871296 = 88375^2 + 102464^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18309011921 is a prime.

It is a super-2 number, since 2×18309011921² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18309011923) 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, 19857470 + ... + 19858391.

It is an arithmetic number, because the mean of its divisors is an integer number (4587182061).

Almost surely, 2^18309011921 is an apocalyptic number.

It is an amenable number.

18309011921 is a deficient number, since it is larger than the sum of its proper divisors (39716323).

18309011921 is an equidigital number, since it uses as much as digits as its factorization.

18309011921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39716322.

The product of its (nonzero) digits is 3888, while the sum is 35.

The spelling of 18309011921 in words is "eighteen billion, three hundred nine million, eleven thousand, nine hundred twenty-one".