18309521 has 4 divisors (see below), whose sum is σ = 19273200. Its totient is φ = 17345844.

The previous prime is 18309509. The next prime is 18309523. The reversal of 18309521 is 12590381.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12590381 = 599 ⋅21019.

It is a cyclic number.

It is not a de Polignac number, because 18309521 - 2⁶ = 18309457 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18309523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 481811 + ... + 481848.

It is an arithmetic number, because the mean of its divisors is an integer number (4818300).

Almost surely, 2^18309521 is an apocalyptic number.

It is an amenable number.

18309521 is a deficient number, since it is larger than the sum of its proper divisors (963679).

18309521 is an equidigital number, since it uses as much as digits as its factorization.

18309521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 963678.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 18309521 is about 4278.9626079226. The cubic root of 18309521 is about 263.5677854669.

The spelling of 18309521 in words is "eighteen million, three hundred nine thousand, five hundred twenty-one".