644791 has 6 divisors (see below), whose sum is σ = 750120. Its totient is φ = 552636.

The previous prime is 644789. The next prime is 644797. The reversal of 644791 is 197446.

644791 = T₁₀ + T₁₁ + ... + T₁₅₆.

It is not a de Polignac number, because 644791 - 2¹ = 644789 is a prime.

644791 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644797) 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 5 ways as a sum of consecutive naturals, for example, 6531 + ... + 6628.

It is an arithmetic number, because the mean of its divisors is an integer number (125020).

2⁶⁴⁴⁷⁹¹ is an apocalyptic number.

644791 is a deficient number, since it is larger than the sum of its proper divisors (105329).

644791 is a wasteful number, since it uses less digits than its factorization.

It is an anagram of its base 13 representation: 644791 = (197644)₁₃.

644791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13173 (or 13166 counting only the distinct ones).

The product of its digits is 6048, while the sum is 31.

The square root of 644791 is about 802.9887919517. The cubic root of 644791 is about 86.3918927435.

The spelling of 644791 in words is "six hundred forty-four thousand, seven hundred ninety-one".