644759 has 12 divisors (see below), whose sum is σ = 722064. Its totient is φ = 574464.

The previous prime is 644753. The next prime is 644767. The reversal of 644759 is 957446.

It is not a de Polignac number, because 644759 - 2¹² = 640663 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 644759.

It is not an unprimeable number, because it can be changed into a prime (644753) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6599 + ... + 6695.

It is an arithmetic number, because the mean of its divisors is an integer number (60172).

2⁶⁴⁴⁷⁵⁹ is an apocalyptic number.

644759 is a deficient number, since it is larger than the sum of its proper divisors (77305).

644759 is a wasteful number, since it uses less digits than its factorization.

644759 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154 (or 137 counting only the distinct ones).

The product of its digits is 30240, while the sum is 35.

The square root of 644759 is about 802.9688661461. The cubic root of 644759 is about 86.3904635536.

The spelling of 644759 in words is "six hundred forty-four thousand, seven hundred fifty-nine".