18439621 has 4 divisors (see below), whose sum is σ = 19075500. Its totient is φ = 17803744.

The previous prime is 18439609. The next prime is 18439649. The reversal of 18439621 is 12693481.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12693481 = 821 ⋅15461.

It can be written as a sum of positive squares in 2 ways, for example, as 8767521 + 9672100 = 2961^2 + 3110^2 .

It is a cyclic number.

It is not a de Polignac number, because 18439621 - 2¹⁵ = 18406853 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18439321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 317896 + ... + 317953.

It is an arithmetic number, because the mean of its divisors is an integer number (4768875).

Almost surely, 2^18439621 is an apocalyptic number.

It is an amenable number.

18439621 is a deficient number, since it is larger than the sum of its proper divisors (635879).

18439621 is an equidigital number, since it uses as much as digits as its factorization.

18439621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 635878.

The product of its digits is 10368, while the sum is 34.

The square root of 18439621 is about 4294.1379810155. The cubic root of 18439621 is about 264.1905811272.

The spelling of 18439621 in words is "eighteen million, four hundred thirty-nine thousand, six hundred twenty-one".