644664173 has 4 divisors (see below), whose sum is σ = 658380480. Its totient is φ = 630947868.

The previous prime is 644664169. The next prime is 644664199. The reversal of 644664173 is 371466446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 644664173 - 2² = 644664169 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644664173.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644664143) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6858083 + ... + 6858176.

It is an arithmetic number, because the mean of its divisors is an integer number (164595120).

Almost surely, 2^644664173 is an apocalyptic number.

It is an amenable number.

644664173 is a deficient number, since it is larger than the sum of its proper divisors (13716307).

644664173 is a wasteful number, since it uses less digits than its factorization.

644664173 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13716306.

The product of its digits is 290304, while the sum is 41.

The square root of 644664173 is about 25390.2377499700. The cubic root of 644664173 is about 863.8622809505.

The spelling of 644664173 in words is "six hundred forty-four million, six hundred sixty-four thousand, one hundred seventy-three".