644421912576 has 768 divisors, whose sum is σ = 2047897313280. Its totient is φ = 178362777600.

The previous prime is 644421912527. The next prime is 644421912587. The reversal of 644421912576 is 675219124446.

It is a tau number, because it is divible by the number of its divisors (768).

It is a Harshad number since it is a multiple of its sum of digits (51).

Its product of digits (2903040) is a multiple of the sum of its prime factors (320).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 5074188225 + ... + 5074188351.

It is an arithmetic number, because the mean of its divisors is an integer number (2666532960).

Almost surely, 2^644421912576 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 644421912576, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1023948656640).

644421912576 is an abundant number, since it is smaller than the sum of its proper divisors (1403475400704).

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

644421912576 is a wasteful number, since it uses less digits than its factorization.

644421912576 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320 (or 300 counting only the distinct ones).

The product of its digits is 2903040, while the sum is 51.

The spelling of 644421912576 in words is "six hundred forty-four billion, four hundred twenty-one million, nine hundred twelve thousand, five hundred seventy-six".