644817223 has 4 divisors (see below), whose sum is σ = 646425648. Its totient is φ = 643208800.

The previous prime is 644817181. The next prime is 644817311. The reversal of 644817223 is 322718446.

644817223 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644817223 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 (644817023) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 803611 + ... + 804412.

It is an arithmetic number, because the mean of its divisors is an integer number (161606412).

Almost surely, 2^644817223 is an apocalyptic number.

644817223 is a deficient number, since it is larger than the sum of its proper divisors (1608425).

644817223 is a wasteful number, since it uses less digits than its factorization.

644817223 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1608424.

The product of its digits is 64512, while the sum is 37.

The square root of 644817223 is about 25393.2515247654. The cubic root of 644817223 is about 863.9306388470.

The spelling of 644817223 in words is "six hundred forty-four million, eight hundred seventeen thousand, two hundred twenty-three".