644004817 has 4 divisors (see below), whose sum is σ = 644068260. Its totient is φ = 643941376.

The previous prime is 644004799. The next prime is 644004887. The reversal of 644004817 is 718400446.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 339886096 + 304118721 = 18436^2 + 17439^2 .

It is a 3-Lehmer number, since φ(644004817) divides (644004817-1)³.

It is a cyclic number.

It is not a de Polignac number, because 644004817 - 2⁷ = 644004689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644004887) 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, 12688 + ... + 38065.

It is an arithmetic number, because the mean of its divisors is an integer number (161017065).

It is a Poulet number, since it divides 2^644004816-1.

Almost surely, 2^644004817 is an apocalyptic number.

644004817 is the 12689-th decagonal number.

It is an amenable number.

644004817 is a deficient number, since it is larger than the sum of its proper divisors (63443).

644004817 is a wasteful number, since it uses less digits than its factorization.

644004817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63442.

The product of its (nonzero) digits is 21504, while the sum is 34.

The square root of 644004817 is about 25377.2499889172. The cubic root of 644004817 is about 863.5676639475.

The spelling of 644004817 in words is "six hundred forty-four million, four thousand, eight hundred seventeen".