18666 has 24 divisors (see below), whose sum is σ = 43524. Its totient is φ = 5760.

The previous prime is 18661. The next prime is 18671. The reversal of 18666 is 66681.

It is an interprime number because it is at equal distance from previous prime (18661) and next prime (18671).

It can be written as a sum of positive squares in 2 ways, for example, as 18225 + 441 = 135^2 + 21^2 .

18666 is a modest number, since divided by 666 gives 18 as remainder.

It is a nialpdrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (18661) 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 in 11 ways as a sum of consecutive naturals, for example, 276 + ... + 336.

2¹⁸⁶⁶⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21762).

18666 is an abundant number, since it is smaller than the sum of its proper divisors (24858).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18666 is a wasteful number, since it uses less digits than its factorization.

18666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86 (or 83 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 18666 is about 136.6235704408. The cubic root of 18666 is about 26.5267322507.

It can be divided in two parts, 186 and 66, that added together give a palindrome (252).

The spelling of 18666 in words is "eighteen thousand, six hundred sixty-six".