18865621 has 4 divisors (see below), whose sum is σ = 18925452. Its totient is φ = 18805792.

The previous prime is 18865619. The next prime is 18865661. The reversal of 18865621 is 12656881.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 280900 + 18584721 = 530^2 + 4311^2 .

It is a cyclic number.

It is not a de Polignac number, because 18865621 - 2¹ = 18865619 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 (18865661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29440 + ... + 30073.

It is an arithmetic number, because the mean of its divisors is an integer number (4731363).

Almost surely, 2^18865621 is an apocalyptic number.

It is an amenable number.

18865621 is a deficient number, since it is larger than the sum of its proper divisors (59831).

18865621 is an equidigital number, since it uses as much as digits as its factorization.

18865621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59830.

The product of its digits is 23040, while the sum is 37.

The square root of 18865621 is about 4343.4572635172. The cubic root of 18865621 is about 266.2095932274.

The spelling of 18865621 in words is "eighteen million, eight hundred sixty-five thousand, six hundred twenty-one".