644375 has 10 divisors (see below), whose sum is σ = 805992. Its totient is φ = 515000.

The previous prime is 644363. The next prime is 644377. The reversal of 644375 is 573446.

It is not a de Polignac number, because 644375 - 2⁴ = 644359 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 644375.

It is not an unprimeable number, because it can be changed into a prime (644377) 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 9 ways as a sum of consecutive naturals, for example, 110 + ... + 1140.

2⁶⁴⁴³⁷⁵ is an apocalyptic number.

644375 is a deficient number, since it is larger than the sum of its proper divisors (161617).

644375 is an equidigital number, since it uses as much as digits as its factorization.

644375 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1051 (or 1036 counting only the distinct ones).

The product of its digits is 10080, while the sum is 29.

The square root of 644375 is about 802.7297179001. The cubic root of 644375 is about 86.3733095855.

The spelling of 644375 in words is "six hundred forty-four thousand, three hundred seventy-five".