644068758436 has 6 divisors (see below), whose sum is σ = 1127120327270. Its totient is φ = 322034379216.

The previous prime is 644068758419. The next prime is 644068758439. The reversal of 644068758436 is 634857860446.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 488601000000 + 155467758436 = 699000^2 + 394294^2 .

It is not an unprimeable number, because it can be changed into a prime (644068758439) 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 as a sum of consecutive naturals, namely, 80508594801 + ... + 80508594808.

Almost surely, 2^644068758436 is an apocalyptic number.

It is an amenable number.

644068758436 is a deficient number, since it is larger than the sum of its proper divisors (483051568834).

644068758436 is a wasteful number, since it uses less digits than its factorization.

644068758436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161017189613 (or 161017189611 counting only the distinct ones).

The product of its (nonzero) digits is 92897280, while the sum is 61.

The spelling of 644068758436 in words is "six hundred forty-four billion, sixty-eight million, seven hundred fifty-eight thousand, four hundred thirty-six".