644264 has 16 divisors (see below), whose sum is σ = 1250100. Its totient is φ = 310912.

The previous prime is 644261. The next prime is 644291. The reversal of 644264 is 462446.

It can be written as a sum of positive squares in 2 ways, for example, as 624100 + 20164 = 790^2 + 142^2 .

It is a super-2 number, since 2×644264² = 830152203392, which contains 22 as substring.

It is a d-powerful number, because it can be written as 6⁵ + 4 + 2¹⁹ + 4 + 6⁶ + 4⁸ .

It is not an unprimeable number, because it can be changed into a prime (644261) 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, 1157 + ... + 1620.

2⁶⁴⁴²⁶⁴ is an apocalyptic number.

It is an amenable number.

644264 is a deficient number, since it is larger than the sum of its proper divisors (605836).

644264 is a wasteful number, since it uses less digits than its factorization.

644264 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2812 (or 2808 counting only the distinct ones).

The product of its digits is 4608, while the sum is 26.

The square root of 644264 is about 802.6605758351. The cubic root of 644264 is about 86.3683497470.

The spelling of 644264 in words is "six hundred forty-four thousand, two hundred sixty-four".