19866 has 32 divisors (see below), whose sum is σ = 50688. Its totient is φ = 5040.

The previous prime is 19861. The next prime is 19867. The reversal of 19866 is 66891.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19861) by changing a digit.

19866 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 15 ways as a sum of consecutive naturals, for example, 441 + ... + 483.

It is an arithmetic number, because the mean of its divisors is an integer number (1584).

2¹⁹⁸⁶⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19866, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25344).

19866 is an abundant number, since it is smaller than the sum of its proper divisors (30822).

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

19866 is a wasteful number, since it uses less digits than its factorization.

19866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66.

The product of its digits is 2592, while the sum is 30.

The square root of 19866 is about 140.9467984738. The cubic root of 19866 is about 27.0834182772.

The spelling of 19866 in words is "nineteen thousand, eight hundred sixty-six".