644800 has 84 divisors (see below), whose sum is σ = 1763776. Its totient is φ = 230400.

The previous prime is 644797. The next prime is 644801. The reversal of 644800 is 8446.

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

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 20785 + ... + 20815.

2⁶⁴⁴⁸⁰⁰ 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 644800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (881888).

644800 is an abundant number, since it is smaller than the sum of its proper divisors (1118976).

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

644800 is a wasteful number, since it uses less digits than its factorization.

644800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66 (or 51 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 22.

The square root of 644800 is about 802.9943959954. The cubic root of 644800 is about 86.3922946946.

It can be divided in two parts, 644 and 800, that added together give a square (1444 = 38²).

The spelling of 644800 in words is "six hundred forty-four thousand, eight hundred".