664866 has 24 divisors (see below), whose sum is σ = 1475760. Its totient is φ = 216216.

The previous prime is 664849. The next prime is 664879. The reversal of 664866 is 668466.

664866 is a `hidden beast` number, since 6 + 648 + 6 + 6 = 666.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 664866.

It is an unprimeable number.

664866 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 345 + ... + 1203.

It is an arithmetic number, because the mean of its divisors is an integer number (61490).

2⁶⁶⁴⁸⁶⁶ is an apocalyptic number.

664866 is the 516-th heptagonal number.

664866 is an abundant number, since it is smaller than the sum of its proper divisors (810894).

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

664866 is a wasteful number, since it uses less digits than its factorization.

664866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 910 (or 907 counting only the distinct ones).

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

The square root of 664866 is about 815.3931567042. The cubic root of 664866 is about 87.2793241936.

Subtracting 664866 from its reverse (668466), we obtain a square (3600 = 60²).

The spelling of 664866 in words is "six hundred sixty-four thousand, eight hundred sixty-six".