644764107322368 has 1056 divisors, whose sum is σ = 2127001271915520. Its totient is φ = 186412264980480.

The previous prime is 644764107322331. The next prime is 644764107322381. The reversal of 644764107322368 is 863223701467446.

644764107322368 is a `hidden beast` number, since 6 + 4 + 4 + 76 + 410 + 73 + 2 + 23 + 68 = 666.

It is a tau number, because it is divible by the number of its divisors (1056).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 32201164005 + ... + 32201184027.

It is an arithmetic number, because the mean of its divisors is an integer number (2014205749920).

Almost surely, 2^{644764107322368} 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 644764107322368, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1063500635957760).

644764107322368 is an abundant number, since it is smaller than the sum of its proper divisors (1482237164593152).

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

644764107322368 is a wasteful number, since it uses less digits than its factorization.

644764107322368 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20275 (or 20254 counting only the distinct ones).

The product of its (nonzero) digits is 195084288, while the sum is 63.

The spelling of 644764107322368 in words is "six hundred forty-four trillion, seven hundred sixty-four billion, one hundred seven million, three hundred twenty-two thousand, three hundred sixty-eight".