644823 has 6 divisors (see below), whose sum is σ = 931424. Its totient is φ = 429876.

The previous prime is 644801. The next prime is 644837. The reversal of 644823 is 328446.

It is not a de Polignac number, because 644823 - 2¹² = 640727 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644823.

It is not an unprimeable number, because it can be changed into a prime (644843) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35815 + ... + 35832.

2⁶⁴⁴⁸²³ is an apocalyptic number.

644823 is a deficient number, since it is larger than the sum of its proper divisors (286601).

644823 is a wasteful number, since it uses less digits than its factorization.

644823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71653 (or 71650 counting only the distinct ones).

The product of its digits is 4608, while the sum is 27.

The square root of 644823 is about 803.0087172628. The cubic root of 644823 is about 86.3933218861.

The spelling of 644823 in words is "six hundred forty-four thousand, eight hundred twenty-three".