644285 has 4 divisors (see below), whose sum is σ = 773148. Its totient is φ = 515424.

The previous prime is 644261. The next prime is 644291. The reversal of 644285 is 582446.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 376996 + 267289 = 614^2 + 517^2 .

It is a cyclic number.

It is not a de Polignac number, because 644285 - 2⁸ = 644029 is a prime.

It is a super-2 number, since 2×644285² = 830206322450, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64424 + ... + 64433.

It is an arithmetic number, because the mean of its divisors is an integer number (193287).

2⁶⁴⁴²⁸⁵ is an apocalyptic number.

It is an amenable number.

644285 is a deficient number, since it is larger than the sum of its proper divisors (128863).

644285 is a wasteful number, since it uses less digits than its factorization.

644285 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128862.

The product of its digits is 7680, while the sum is 29.

The square root of 644285 is about 802.6736572232. The cubic root of 644285 is about 86.3692881385.

It can be divided in two parts, 644 and 285, that added together give a palindrome (929).

The spelling of 644285 in words is "six hundred forty-four thousand, two hundred eighty-five".