18866 has 4 divisors (see below), whose sum is σ = 28302. Its totient is φ = 9432.

The previous prime is 18859. The next prime is 18869. The reversal of 18866 is 66881.

18866 = 34² + 35² + ... + 45².

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 66881 = 47 ⋅1423.

It can be written as a sum of positive squares in only one way, i.e., 14641 + 4225 = 121^2 + 65^2 .

It is not an unprimeable number, because it can be changed into a prime (18869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4715 + ... + 4718.

2¹⁸⁸⁶⁶ is an apocalyptic number.

18866 is a deficient number, since it is larger than the sum of its proper divisors (9436).

18866 is an equidigital number, since it uses as much as digits as its factorization.

18866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9435.

The product of its digits is 2304, while the sum is 29.

The square root of 18866 is about 137.3535583813. The cubic root of 18866 is about 26.6211375884.

The spelling of 18866 in words is "eighteen thousand, eight hundred sixty-six".