644659 has 4 divisors (see below), whose sum is σ = 646360. Its totient is φ = 642960.

The previous prime is 644653. The next prime is 644669. The reversal of 644659 is 956446.

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

It is a cyclic number.

It is not a de Polignac number, because 644659 - 2⁷ = 644531 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644653) 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 3 ways as a sum of consecutive naturals, for example, 7 + ... + 1135.

It is an arithmetic number, because the mean of its divisors is an integer number (161590).

2⁶⁴⁴⁶⁵⁹ is an apocalyptic number.

644659 is a deficient number, since it is larger than the sum of its proper divisors (1701).

644659 is a wasteful number, since it uses less digits than its factorization.

644659 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1700.

The product of its digits is 25920, while the sum is 34.

The square root of 644659 is about 802.9065948166. The cubic root of 644659 is about 86.3859970305.

The spelling of 644659 in words is "six hundred forty-four thousand, six hundred fifty-nine".