644805 has 48 divisors (see below), whose sum is σ = 1347840. Its totient is φ = 278784.

The previous prime is 644801. The next prime is 644837. The reversal of 644805 is 508446.

It is not a de Polignac number, because 644805 - 2² = 644801 is a prime.

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 644805.

It is not an unprimeable number, because it can be changed into a prime (644801) 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 47 ways as a sum of consecutive naturals, for example, 7201 + ... + 7289.

It is an arithmetic number, because the mean of its divisors is an integer number (28080).

2⁶⁴⁴⁸⁰⁵ is an apocalyptic number.

It is an amenable number.

644805 is an abundant number, since it is smaller than the sum of its proper divisors (703035).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644805 is a wasteful number, since it uses less digits than its factorization.

644805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130 (or 127 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 644805 is about 802.9975093361. The cubic root of 644805 is about 86.3925179992.

The spelling of 644805 in words is "six hundred forty-four thousand, eight hundred five".