644995808 has 48 divisors (see below), whose sum is σ = 1343817216. Its totient is φ = 304106880.

The previous prime is 644995783. The next prime is 644995811. The reversal of 644995808 is 808599446.

It is a happy number.

644995808 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 644995808.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 46085 + ... + 58427.

It is an arithmetic number, because the mean of its divisors is an integer number (27996192).

Almost surely, 2^644995808 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 644995808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (671908608).

644995808 is an abundant number, since it is smaller than the sum of its proper divisors (698821408).

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

644995808 is a wasteful number, since it uses less digits than its factorization.

644995808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12447 (or 12439 counting only the distinct ones).

The product of its (nonzero) digits is 2488320, while the sum is 53.

The square root of 644995808 is about 25396.7676683471. The cubic root of 644995808 is about 864.0103879638.

It can be divided in two parts, 64499 and 5808, that added together give a palindrome (70307).

The spelling of 644995808 in words is "six hundred forty-four million, nine hundred ninety-five thousand, eight hundred eight".