644565 has 16 divisors (see below), whose sum is σ = 1044288. Its totient is φ = 339456.

The previous prime is 644563. The next prime is 644569. The reversal of 644565 is 565446.

It is not a de Polignac number, because 644565 - 2¹ = 644563 is a prime.

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 polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1234 + ... + 1676.

It is an arithmetic number, because the mean of its divisors is an integer number (65268).

2⁶⁴⁴⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

644565 is a deficient number, since it is larger than the sum of its proper divisors (399723).

644565 is a wasteful number, since it uses less digits than its factorization.

644565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 548.

The product of its digits is 14400, while the sum is 30.

The square root of 644565 is about 802.8480553629. The cubic root of 644565 is about 86.3817980775.

The spelling of 644565 in words is "six hundred forty-four thousand, five hundred sixty-five".