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18881 = 79239

18881 has 4 divisors (see below), whose sum is σ = 19200. Its totient is φ = 18564.

The previous prime is 18869. The next prime is 18899.

18881 is nontrivially palindromic in base 5 and base 10.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2k-18881 is a prime.

It is a super-2 number, since 2×188812 = 712984322, which contains 22 as substring.

18881 is a strobogrammatic number because it is the same when read upside-down.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18881.

It is not an unprimeable number, because it can be changed into a prime (18181) 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, 41 + ... + 198.

It is an arithmetic number, because the mean of its divisors is an integer number (4800).

218881 is an apocalyptic number.

It is an amenable number.

18881 is a deficient number, since it is larger than the sum of its proper divisors (319).

18881 is an equidigital number, since it uses as much as digits as its factorization.

18881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 318.

The product of its digits is 512, while the sum is 26.

The square root of 18881 is about 137.4081511410. The cubic root of 18881 is about 26.6281910405.

The spelling of 18881 in words is "eighteen thousand, eight hundred eighty-one".

Divisors: 1 79 239 18881