644808 has 32 divisors (see below), whose sum is σ = 1640160. Its totient is φ = 211200.

The previous prime is 644801. The next prime is 644837. The reversal of 644808 is 808446.

644808 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Cunningham number, because it is equal to 803²-1.

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 644808.

It is not an unprimeable number, because it can be changed into a prime (644801) by changing a digit.

644808 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1408 + ... + 1808.

It is an arithmetic number, because the mean of its divisors is an integer number (51255).

2⁶⁴⁴⁸⁰⁸ is an apocalyptic number.

It is an amenable number.

644808 is an abundant number, since it is smaller than the sum of its proper divisors (995352).

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

644808 is a wasteful number, since it uses less digits than its factorization.

644808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 477 (or 473 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 30.

The square root of 644808 is about 802.9993773348. Note that the first 3 decimals coincide. The cubic root of 644808 is about 86.3926519814.

The spelling of 644808 in words is "six hundred forty-four thousand, eight hundred eight".