18109521 has 16 divisors (see below), whose sum is σ = 27155520. Its totient is φ = 11926080.

The previous prime is 18109501. The next prime is 18109547. The reversal of 18109521 is 12590181.

18109521 is nontrivially palindromic in base 2 and base 4.

It is not a de Polignac number, because 18109521 - 2⁶ = 18109457 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (18109501) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1800 + ... + 6281.

It is an arithmetic number, because the mean of its divisors is an integer number (1697220).

Almost surely, 2^18109521 is an apocalyptic number.

It is an amenable number.

18109521 is a deficient number, since it is larger than the sum of its proper divisors (9045999).

18109521 is an equidigital number, since it uses as much as digits as its factorization.

18109521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8173 (or 8167 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 27.

The square root of 18109521 is about 4255.5282868288. The cubic root of 18109521 is about 262.6045950525.

The spelling of 18109521 in words is "eighteen million, one hundred nine thousand, five hundred twenty-one".