644320 has 24 divisors (see below), whose sum is σ = 1522584. Its totient is φ = 257664.

The previous prime is 644297. The next prime is 644327. The reversal of 644320 is 23446.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644327) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1854 + ... + 2173.

It is an arithmetic number, because the mean of its divisors is an integer number (63441).

2⁶⁴⁴³²⁰ is an apocalyptic number.

It is an amenable number.

644320 is an abundant number, since it is smaller than the sum of its proper divisors (878264).

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

644320 is a wasteful number, since it uses less digits than its factorization.

644320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4042 (or 4034 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 19.

The square root of 644320 is about 802.6954590628. The cubic root of 644320 is about 86.3708520791.

Adding to 644320 its reverse (23446), we get a palindrome (667766).

The spelling of 644320 in words is "six hundred forty-four thousand, three hundred twenty".