18321309 has 10 divisors (see below), whose sum is σ = 27368990. Its totient is φ = 12214152.

The previous prime is 18321307. The next prime is 18321313. The reversal of 18321309 is 90312381.

It can be written as a sum of positive squares in only one way, i.e., 17665209 + 656100 = 4203^2 + 810^2 .

It is not a de Polignac number, because 18321309 - 2¹ = 18321307 is a prime.

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

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18321307) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 113014 + ... + 113175.

It is an arithmetic number, because the mean of its divisors is an integer number (2736899).

Almost surely, 2^18321309 is an apocalyptic number.

It is an amenable number.

18321309 is a deficient number, since it is larger than the sum of its proper divisors (9047681).

18321309 is an equidigital number, since it uses as much as digits as its factorization.

18321309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 226201 (or 226192 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 18321309 is about 4280.3398229580. The cubic root of 18321309 is about 263.6243365644.

The spelling of 18321309 in words is "eighteen million, three hundred twenty-one thousand, three hundred nine".