1866 has 8 divisors (see below), whose sum is σ = 3744. Its totient is φ = 620.

The previous prime is 1861. The next prime is 1867. The reversal of 1866 is 6681.

It is a sphenic number, since it is the product of 3 distinct primes.

1866 is an admirable number.

1866 is a modest number, since divided by 66 gives 18 as remainder.

It is a Curzon number.

It is a plaindrome in base 11.

It is a nialpdrome in base 14.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 1866.

It is not an unprimeable number, because it can be changed into a prime (1861) by changing a digit.

1866 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 150 + ... + 161.

It is an arithmetic number, because the mean of its divisors is an integer number (468).

2¹⁸⁶⁶ is an apocalyptic number.

1866 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1872).

1866 is a wasteful number, since it uses less digits than its factorization.

1866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 316.

The product of its digits is 288, while the sum is 21.

The square root of 1866 is about 43.1972221329. The cubic root of 1866 is about 12.3112990231.

The spelling of 1866 in words is "one thousand, eight hundred sixty-six".