644839 has 4 divisors (see below), whose sum is σ = 694456. Its totient is φ = 595224.

The previous prime is 644837. The next prime is 644843. The reversal of 644839 is 938446.

644839 = T₁₆₂ + T₁₆₃ + ... + T₂₀₀.

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 644839 - 2¹ = 644837 is a prime.

It is a Duffinian number.

644839 is a lucky number.

It is a plaindrome in base 14.

It is a congruent 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 (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24789 + ... + 24814.

It is an arithmetic number, because the mean of its divisors is an integer number (173614).

2⁶⁴⁴⁸³⁹ is an apocalyptic number.

644839 is a deficient number, since it is larger than the sum of its proper divisors (49617).

644839 is a wasteful number, since it uses less digits than its factorization.

644839 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49616.

The product of its digits is 20736, while the sum is 34.

The square root of 644839 is about 803.0186797329. The cubic root of 644839 is about 86.3940364397.

The spelling of 644839 in words is "six hundred forty-four thousand, eight hundred thirty-nine".