18005891 has 4 divisors (see below), whose sum is σ = 18042192. Its totient is φ = 17969592.

The previous prime is 18005881. The next prime is 18005899. The reversal of 18005891 is 19850081.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19850081 = 23 ⋅863047.

It is a cyclic number.

It is not a de Polignac number, because 18005891 - 2¹⁴ = 17989507 is a prime.

It is a super-2 number, since 2×18005891² = 648424221407762, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18005899) 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, 17396 + ... + 18401.

It is an arithmetic number, because the mean of its divisors is an integer number (4510548).

Almost surely, 2^18005891 is an apocalyptic number.

18005891 is a deficient number, since it is larger than the sum of its proper divisors (36301).

18005891 is an equidigital number, since it uses as much as digits as its factorization.

18005891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36300.

The product of its (nonzero) digits is 2880, while the sum is 32.

The square root of 18005891 is about 4243.3348913325. The cubic root of 18005891 is about 262.1027266498.

The spelling of 18005891 in words is "eighteen million, five thousand, eight hundred ninety-one".