644817 has 4 divisors (see below), whose sum is σ = 859760. Its totient is φ = 429876.

The previous prime is 644801. The next prime is 644837. The reversal of 644817 is 718446.

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 not a de Polignac number, because 644817 - 2⁴ = 644801 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644837) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107467 + ... + 107472.

It is an arithmetic number, because the mean of its divisors is an integer number (214940).

2⁶⁴⁴⁸¹⁷ is an apocalyptic number.

It is an amenable number.

644817 is a deficient number, since it is larger than the sum of its proper divisors (214943).

644817 is a wasteful number, since it uses less digits than its factorization.

644817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214942.

The product of its digits is 5376, while the sum is 30.

The square root of 644817 is about 803.0049813046. The cubic root of 644817 is about 86.3930539255.

The spelling of 644817 in words is "six hundred forty-four thousand, eight hundred seventeen".