644402745168 has 480 divisors, whose sum is σ = 2178932539392. Its totient is φ = 162468633600.

The previous prime is 644402745163. The next prime is 644402745257. The reversal of 644402745168 is 861547204446.

It is a self number, because there is not a number n which added to its sum of digits gives 644402745168.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644402745163) 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 95 ways as a sum of consecutive naturals, for example, 78667953 + ... + 78676143.

Almost surely, 2^644402745168 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644402745168, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1089466269696).

644402745168 is an abundant number, since it is smaller than the sum of its proper divisors (1534529794224).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644402745168 is a wasteful number, since it uses less digits than its factorization.

644402745168 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8343 (or 8330 counting only the distinct ones).

The product of its (nonzero) digits is 5160960, while the sum is 51.

The spelling of 644402745168 in words is "six hundred forty-four billion, four hundred two million, seven hundred forty-five thousand, one hundred sixty-eight".