644075 has 6 divisors (see below), whose sum is σ = 798684. Its totient is φ = 515240.

The previous prime is 644057. The next prime is 644089. The reversal of 644075 is 570446.

It is not a de Polignac number, because 644075 - 2¹⁰ = 643051 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 12857 + ... + 12906.

It is an arithmetic number, because the mean of its divisors is an integer number (133114).

2⁶⁴⁴⁰⁷⁵ is an apocalyptic number.

644075 is a deficient number, since it is larger than the sum of its proper divisors (154609).

644075 is a wasteful number, since it uses less digits than its factorization.

644075 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25773 (or 25768 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 26.

The square root of 644075 is about 802.5428337478. The cubic root of 644075 is about 86.3599033054.

The spelling of 644075 in words is "six hundred forty-four thousand, seventy-five".