666864 has 60 divisors (see below), whose sum is σ = 2040792. Its totient is φ = 201600.

The previous prime is 666857. The next prime is 666871. The reversal of 666864 is 468666.

It is an interprime number because it is at equal distance from previous prime (666857) and next prime (666871).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

666864 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 11 ways as a sum of consecutive naturals, for example, 1374 + ... + 1794.

2⁶⁶⁶⁸⁶⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 666864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1020396).

666864 is an abundant number, since it is smaller than the sum of its proper divisors (1373928).

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

666864 is a wasteful number, since it uses less digits than its factorization.

666864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 446 (or 437 counting only the distinct ones).

The product of its digits is 41472, while the sum is 36.

The square root of 666864 is about 816.6174134808. The cubic root of 666864 is about 87.3666649506.

The spelling of 666864 in words is "six hundred sixty-six thousand, eight hundred sixty-four".