644568321 has 16 divisors (see below), whose sum is σ = 869227200. Its totient is φ = 424827648.

The previous prime is 644568299. The next prime is 644568329. The reversal of 644568321 is 123865446.

It is not a de Polignac number, because 644568321 - 2¹³ = 644560129 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644568321.

It is not an unprimeable number, because it can be changed into a prime (644568329) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 180885 + ... + 184413.

It is an arithmetic number, because the mean of its divisors is an integer number (54326700).

Almost surely, 2^644568321 is an apocalyptic number.

It is an amenable number.

644568321 is a deficient number, since it is larger than the sum of its proper divisors (224658879).

644568321 is a wasteful number, since it uses less digits than its factorization.

644568321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4208.

The product of its digits is 138240, while the sum is 39.

The square root of 644568321 is about 25388.3501039355. The cubic root of 644568321 is about 863.8194643260.

The spelling of 644568321 in words is "six hundred forty-four million, five hundred sixty-eight thousand, three hundred twenty-one".