399664 has 10 divisors (see below), whose sum is σ = 774380. Its totient is φ = 199824.

The previous prime is 399647. The next prime is 399667. The reversal of 399664 is 466993.

It is not an unprimeable number, because it can be changed into a prime (399667) by changing a digit.

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 as a sum of consecutive naturals, namely, 12474 + ... + 12505.

It is an arithmetic number, because the mean of its divisors is an integer number (77438).

2³⁹⁹⁶⁶⁴ is an apocalyptic number.

It is an amenable number.

399664 is a deficient number, since it is larger than the sum of its proper divisors (374716).

399664 is a wasteful number, since it uses less digits than its factorization.

399664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24987 (or 24981 counting only the distinct ones).

The product of its digits is 34992, while the sum is 37.

The square root of 399664 is about 632.1898449042. The cubic root of 399664 is about 73.6599936172.

The spelling of 399664 in words is "three hundred ninety-nine thousand, six hundred sixty-four".