644629718969 has 4 divisors (see below), whose sum is σ = 662052143844. Its totient is φ = 627207294096.

The previous prime is 644629718933. The next prime is 644629718987. The reversal of 644629718969 is 969817926446.

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

It can be written as a sum of positive squares in 2 ways, for example, as 526147129600 + 118482589369 = 725360^2 + 344213^2 .

It is a cyclic number.

It is not a de Polignac number, because 644629718969 - 2⁸ = 644629718713 is a prime.

It is a super-2 number, since 2×644629718969² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644629718869) 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, 8711212382 + ... + 8711212455.

It is an arithmetic number, because the mean of its divisors is an integer number (165513035961).

Almost surely, 2^644629718969 is an apocalyptic number.

It is an amenable number.

644629718969 is a deficient number, since it is larger than the sum of its proper divisors (17422424875).

644629718969 is a wasteful number, since it uses less digits than its factorization.

644629718969 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17422424874.

The product of its digits is 282175488, while the sum is 71.

The spelling of 644629718969 in words is "six hundred forty-four billion, six hundred twenty-nine million, seven hundred eighteen thousand, nine hundred sixty-nine".