644890868544 has 224 divisors, whose sum is σ = 1849068224640. Its totient is φ = 197185241088.

The previous prime is 644890868527. The next prime is 644890868563. The reversal of 644890868544 is 445868098446.

644890868544 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 457693312 + ... + 457694720.

It is an arithmetic number, because the mean of its divisors is an integer number (8254768860).

Almost surely, 2^644890868544 is an apocalyptic number.

644890868544 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644890868544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (924534112320).

644890868544 is an abundant number, since it is smaller than the sum of its proper divisors (1204177356096).

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

644890868544 is a wasteful number, since it uses less digits than its factorization.

644890868544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2457 (or 2447 counting only the distinct ones).

The product of its (nonzero) digits is 212336640, while the sum is 66.

The spelling of 644890868544 in words is "six hundred forty-four billion, eight hundred ninety million, eight hundred sixty-eight thousand, five hundred forty-four".