18439321 has 2 divisors, whose sum is σ = 18439322. Its totient is φ = 18439320.

The previous prime is 18439319. The next prime is 18439349. The reversal of 18439321 is 12393481.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16646400 + 1792921 = 4080^2 + 1339^2 .

It is a cyclic number.

It is not a de Polignac number, because 18439321 - 2¹ = 18439319 is a prime.

Together with 18439319, it forms a pair of twin primes.

It is equal to p_1177582 and since 18439321 and 1177582 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (18439361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9219660 + 9219661.

It is an arithmetic number, because the mean of its divisors is an integer number (9219661).

Almost surely, 2^18439321 is an apocalyptic number.

It is an amenable number.

18439321 is a deficient number, since it is larger than the sum of its proper divisors (1).

18439321 is an equidigital number, since it uses as much as digits as its factorization.

18439321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 31.

The square root of 18439321 is about 4294.1030495320. The cubic root of 18439321 is about 264.1891483861.

The spelling of 18439321 in words is "eighteen million, four hundred thirty-nine thousand, three hundred twenty-one".