18817 has 4 divisors (see below), whose sum is σ = 19456.
Its totient is φ = 18180.
The previous prime is 18803. The next prime is 18839. The reversal of 18817 is 71881.
It can be divided in two parts, 18 and 817, that multiplied together give a triangular number (14706 = T171).
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-18817 is a prime.
It is a Duffinian number.
18817 is a lucky number.
It is a nialpdrome in base 12.
It is a junction number, because it is equal to n+sod(n) for n = 18791 and 18800.
It is not an unprimeable number, because it can be changed into a prime (18217) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (5) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 273 + ... + 334.
It is an arithmetic number, because the mean of its divisors is an integer number (4864).
218817 is an apocalyptic number.
It is an amenable number.
18817 is a deficient number, since it is larger than the sum of its proper divisors (639).
18817 is an equidigital number, since it uses as much as digits as its factorization.
18817 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 638.
The product of its digits is 448, while the sum is 25.
The square root of 18817 is about 137.1750706215.
The cubic root of 18817 is about 26.5980702239.
The spelling of 18817 in words is "eighteen thousand, eight hundred seventeen".