18221587 has 4 divisors (see below), whose sum is σ = 18452320. Its totient is φ = 17990856.

The previous prime is 18221563. The next prime is 18221611. The reversal of 18221587 is 78512281.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 78512281 = 43 ⋅1825867.

It is an interprime number because it is at equal distance from previous prime (18221563) and next prime (18221611).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18221587 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18221527) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 115248 + ... + 115405.

It is an arithmetic number, because the mean of its divisors is an integer number (4613080).

Almost surely, 2^18221587 is an apocalyptic number.

18221587 is a deficient number, since it is larger than the sum of its proper divisors (230733).

18221587 is an equidigital number, since it uses as much as digits as its factorization.

18221587 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 230732.

The product of its digits is 8960, while the sum is 34.

The square root of 18221587 is about 4268.6750871904. The cubic root of 18221587 is about 263.1451679691.

The spelling of 18221587 in words is "eighteen million, two hundred twenty-one thousand, five hundred eighty-seven".