18861 has 4 divisors (see below), whose sum is σ = 25152.
Its totient is φ = 12572.
The previous prime is 18859. The next prime is 18869. The reversal of 18861 is 16881.
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 not a de Polignac number, because 18861 - 21 = 18859 is a prime.
It is a D-number.
It is a plaindrome in base 16.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (18869) 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, 3141 + ... + 3146.
It is an arithmetic number, because the mean of its divisors is an integer number (6288).
218861 is an apocalyptic number.
It is an amenable number.
18861 is a deficient number, since it is larger than the sum of its proper divisors (6291).
18861 is an equidigital number, since it uses as much as digits as its factorization.
18861 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 6290.
The product of its digits is 384, while the sum is 24.
The square root of 18861 is about 137.3353559722.
The cubic root of 18861 is about 26.6187856069.
The spelling of 18861 in words is "eighteen thousand, eight hundred sixty-one".