18659881 has 4 divisors (see below), whose sum is σ = 19642000. Its totient is φ = 17677764.

The previous prime is 18659873. The next prime is 18659891. The reversal of 18659881 is 18895681.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18895681 = 7 ⋅2699383.

It is a cyclic number.

It is not a de Polignac number, because 18659881 - 2³ = 18659873 is a prime.

It is a super-2 number, since 2×18659881² = 696382317868322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18659801) 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, 491031 + ... + 491068.

It is an arithmetic number, because the mean of its divisors is an integer number (4910500).

Almost surely, 2^18659881 is an apocalyptic number.

It is an amenable number.

18659881 is a deficient number, since it is larger than the sum of its proper divisors (982119).

18659881 is an equidigital number, since it uses as much as digits as its factorization.

18659881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 982118.

The product of its digits is 138240, while the sum is 46.

The square root of 18659881 is about 4319.7084392352. The cubic root of 18659881 is about 265.2383331118.

The spelling of 18659881 in words is "eighteen million, six hundred fifty-nine thousand, eight hundred eighty-one".