644885 has 8 divisors (see below), whose sum is σ = 782136. Its totient is φ = 510400.

The previous prime is 644881. The next prime is 644899. The reversal of 644885 is 588446.

It can be written as a sum of positive squares in 4 ways, for example, as 264196 + 380689 = 514^2 + 617^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 644885 - 2² = 644881 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644885.

It is not an unprimeable number, because it can be changed into a prime (644881) 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 in 7 ways as a sum of consecutive naturals, for example, 134 + ... + 1143.

It is an arithmetic number, because the mean of its divisors is an integer number (97767).

2⁶⁴⁴⁸⁸⁵ is an apocalyptic number.

It is an amenable number.

644885 is a deficient number, since it is larger than the sum of its proper divisors (137251).

644885 is a wasteful number, since it uses less digits than its factorization.

644885 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1383.

The product of its digits is 30720, while the sum is 35.

The square root of 644885 is about 803.0473211461. The cubic root of 644885 is about 86.3960907153.

The spelling of 644885 in words is "six hundred forty-four thousand, eight hundred eighty-five".