644594131621439 has 4 divisors (see below), whose sum is σ = 645772548681624. Its totient is φ = 643415714561256.

The previous prime is 644594131621409. The next prime is 644594131621469. The reversal of 644594131621439 is 934126131495446.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (644594131621409) and next prime (644594131621469).

It is a cyclic number.

It is not a de Polignac number, because 644594131621439 - 2⁸ = 644594131621183 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644594131621409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 589208529272 + ... + 589208530365.

It is an arithmetic number, because the mean of its divisors is an integer number (161443137170406).

Almost surely, 2^{644594131621439} is an apocalyptic number.

644594131621439 is a deficient number, since it is larger than the sum of its proper divisors (1178417060185).

644594131621439 is a wasteful number, since it uses less digits than its factorization.

644594131621439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1178417060184.

The product of its digits is 67184640, while the sum is 62.

The spelling of 644594131621439 in words is "six hundred forty-four trillion, five hundred ninety-four billion, one hundred thirty-one million, six hundred twenty-one thousand, four hundred thirty-nine".