644564 has 6 divisors (see below), whose sum is σ = 1127994. Its totient is φ = 322280.

The previous prime is 644563. The next prime is 644569. The reversal of 644564 is 465446.

It can be written as a sum of positive squares in only one way, i.e., 432964 + 211600 = 658^2 + 460^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80567 + ... + 80574.

It is an arithmetic number, because the mean of its divisors is an integer number (187999).

2⁶⁴⁴⁵⁶⁴ is an apocalyptic number.

It is an amenable number.

644564 is a deficient number, since it is larger than the sum of its proper divisors (483430).

644564 is a wasteful number, since it uses less digits than its factorization.

644564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161145 (or 161143 counting only the distinct ones).

The product of its digits is 11520, while the sum is 29.

The square root of 644564 is about 802.8474325798. The cubic root of 644564 is about 86.3817534056.

The spelling of 644564 in words is "six hundred forty-four thousand, five hundred sixty-four".