666664 has 16 divisors (see below), whose sum is σ = 1260000. Its totient is φ = 330672.

The previous prime is 666649. The next prime is 666667. The reversal of 666664 is 466666.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (666667) by changing a digit.

666664 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 3 ways as a sum of consecutive naturals, for example, 1087 + ... + 1585.

It is an arithmetic number, because the mean of its divisors is an integer number (78750).

2⁶⁶⁶⁶⁶⁴ is an apocalyptic number.

It is an amenable number.

666664 is a deficient number, since it is larger than the sum of its proper divisors (593336).

666664 is a wasteful number, since it uses less digits than its factorization.

666664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 672 (or 668 counting only the distinct ones).

The product of its digits is 31104, while the sum is 34.

The square root of 666664 is about 816.4949479329. The cubic root of 666664 is about 87.3579299961.

It can be divided in two parts, 6666 and 64, that multiplied together give a palindrome (426624).

The spelling of 666664 in words is "six hundred sixty-six thousand, six hundred sixty-four".