664209 has 24 divisors (see below), whose sum is σ = 1182272. Its totient is φ = 349920.

The previous prime is 664199. The next prime is 664211. The reversal of 664209 is 902466.

It is not a de Polignac number, because 664209 - 2⁴ = 664193 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (664289) 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 in 23 ways as a sum of consecutive naturals, for example, 414 + ... + 1224.

2⁶⁶⁴²⁰⁹ is an apocalyptic number.

It is an amenable number.

664209 is a deficient number, since it is larger than the sum of its proper divisors (518063).

664209 is a wasteful number, since it uses less digits than its factorization.

664209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 837 (or 834 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 664209 is about 814.9901839900. The cubic root of 664209 is about 87.2505658100.

The spelling of 664209 in words is "six hundred sixty-four thousand, two hundred nine".