644265959 has 4 divisors (see below), whose sum is σ = 645364104. Its totient is φ = 643167816.

The previous prime is 644265917. The next prime is 644265961. The reversal of 644265959 is 959562446.

It is a happy number.

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 644265959 - 2²⁰ = 643217383 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644265659) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 548192 + ... + 549365.

It is an arithmetic number, because the mean of its divisors is an integer number (161341026).

Almost surely, 2^644265959 is an apocalyptic number.

644265959 is a deficient number, since it is larger than the sum of its proper divisors (1098145).

644265959 is a wasteful number, since it uses less digits than its factorization.

644265959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1098144.

The product of its digits is 2332800, while the sum is 50.

The square root of 644265959 is about 25382.3946663824. The cubic root of 644265959 is about 863.6843728634.

The spelling of 644265959 in words is "six hundred forty-four million, two hundred sixty-five thousand, nine hundred fifty-nine".