644620896 has 96 divisors (see below), whose sum is σ = 1886976000. Its totient is φ = 214093440.

The previous prime is 644620891. The next prime is 644620939. The reversal of 644620896 is 698026446.

It is a tau number, because it is divible by the number of its divisors (96).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644620891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 267505 + ... + 269903.

It is an arithmetic number, because the mean of its divisors is an integer number (19656000).

Almost surely, 2^644620896 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 644620896, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (943488000).

644620896 is an abundant number, since it is smaller than the sum of its proper divisors (1242355104).

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

644620896 is a wasteful number, since it uses less digits than its factorization.

644620896 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2729 (or 2715 counting only the distinct ones).

The product of its (nonzero) digits is 497664, while the sum is 45.

The square root of 644620896 is about 25389.3854986685. The cubic root of 644620896 is about 863.8429498496.

The spelling of 644620896 in words is "six hundred forty-four million, six hundred twenty thousand, eight hundred ninety-six".