644644993720 has 768 divisors, whose sum is σ = 1979474112000. Its totient is φ = 186646892544.

The previous prime is 644644993711. The next prime is 644644993771. The reversal of 644644993720 is 27399446446.

It is a congruent number.

It is an unprimeable number.

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 in 191 ways as a sum of consecutive naturals, for example, 3601368591 + ... + 3601368769.

It is an arithmetic number, because the mean of its divisors is an integer number (2577440250).

Almost surely, 2^644644993720 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 644644993720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (989737056000).

644644993720 is an abundant number, since it is smaller than the sum of its proper divisors (1334829118280).

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

644644993720 is a wasteful number, since it uses less digits than its factorization.

644644993720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 452 (or 441 counting only the distinct ones).

The product of its (nonzero) digits is 31352832, while the sum is 58.

The spelling of 644644993720 in words is "six hundred forty-four billion, six hundred forty-four million, nine hundred ninety-three thousand, seven hundred twenty".