999664 has 20 divisors (see below), whose sum is σ = 1983256. Its totient is φ = 487872.

The previous prime is 999653. The next prime is 999667. The reversal of 999664 is 466999.

It is a happy number.

It is a super-2 number, since 2×999664² = 1998656225792, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (43).

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 999664.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39 + ... + 1414.

2⁹⁹⁹⁶⁶⁴ is an apocalyptic number.

It is an amenable number.

999664 is a deficient number, since it is larger than the sum of its proper divisors (983592).

999664 is a wasteful number, since it uses less digits than its factorization.

999664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1504 (or 1498 counting only the distinct ones).

The product of its digits is 104976, while the sum is 43.

The square root of 999664 is about 999.8319858856. The cubic root of 999664 is about 99.9887987454.

The spelling of 999664 in words is "nine hundred ninety-nine thousand, six hundred sixty-four".