644844 has 48 divisors (see below), whose sum is σ = 1663200. Its totient is φ = 193536.

The previous prime is 644843. The next prime is 644857. The reversal of 644844 is 448446.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644844.

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

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5862 + ... + 5970.

It is an arithmetic number, because the mean of its divisors is an integer number (34650).

2⁶⁴⁴⁸⁴⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644844, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (831600).

644844 is an abundant number, since it is smaller than the sum of its proper divisors (1018356).

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

644844 is a wasteful number, since it uses less digits than its factorization.

644844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162 (or 160 counting only the distinct ones).

The product of its digits is 12288, while the sum is 30.

The square root of 644844 is about 803.0217929795. The cubic root of 644844 is about 86.3942597352.

It can be divided in two parts, 6 and 44844, that added together give a triangular number (44850 = T₂₉₉).

The spelling of 644844 in words is "six hundred forty-four thousand, eight hundred forty-four".