644318281839 has 16 divisors (see below), whose sum is σ = 864832872704. Its totient is φ = 426674952000.

The previous prime is 644318281787. The next prime is 644318281891. The reversal of 644318281839 is 938182813446.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (644318281787) and next prime (644318281891).

It is not a de Polignac number, because 644318281839 - 2⁸ = 644318281583 is a prime.

It is a super-2 number, since 2×644318281839² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644318241839) 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 15 ways as a sum of consecutive naturals, for example, 10011387 + ... + 10075539.

It is an arithmetic number, because the mean of its divisors is an integer number (54052054544).

Almost surely, 2^644318281839 is an apocalyptic number.

644318281839 is a deficient number, since it is larger than the sum of its proper divisors (220514590865).

644318281839 is a wasteful number, since it uses less digits than its factorization.

644318281839 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86478.

The product of its digits is 7962624, while the sum is 57.

The spelling of 644318281839 in words is "six hundred forty-four billion, three hundred eighteen million, two hundred eighty-one thousand, eight hundred thirty-nine".