644752638160 has 80 divisors (see below), whose sum is σ = 1520619192000. Its totient is φ = 254195020800.

The previous prime is 644752638083. The next prime is 644752638227. The reversal of 644752638160 is 61836257446.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 644752638098 and 644752638107.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8717335 + ... + 8790985.

It is an arithmetic number, because the mean of its divisors is an integer number (19007739900).

Almost surely, 2^644752638160 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 644752638160, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (760309596000).

644752638160 is an abundant number, since it is smaller than the sum of its proper divisors (875866553840).

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

644752638160 is a wasteful number, since it uses less digits than its factorization.

644752638160 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75236 (or 75230 counting only the distinct ones).

The product of its (nonzero) digits is 5806080, while the sum is 52.

The spelling of 644752638160 in words is "six hundred forty-four billion, seven hundred fifty-two million, six hundred thirty-eight thousand, one hundred sixty".