664823 has 4 divisors (see below), whose sum is σ = 680328. Its totient is φ = 649320.

The previous prime is 664799. The next prime is 664843. The reversal of 664823 is 328466.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 328466 = 2 ⋅164233.

It is a cyclic number.

It is not a de Polignac number, because 664823 - 2¹² = 660727 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664843) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7688 + ... + 7773.

It is an arithmetic number, because the mean of its divisors is an integer number (170082).

2⁶⁶⁴⁸²³ is an apocalyptic number.

664823 is a deficient number, since it is larger than the sum of its proper divisors (15505).

664823 is a wasteful number, since it uses less digits than its factorization.

664823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15504.

The product of its digits is 6912, while the sum is 29.

The square root of 664823 is about 815.3667886295. The cubic root of 664823 is about 87.2774425654.

The spelling of 664823 in words is "six hundred sixty-four thousand, eight hundred twenty-three".