644108928 has 128 divisors (see below), whose sum is σ = 1798692480. Its totient is φ = 203833344.

The previous prime is 644108897. The next prime is 644108957. The reversal of 644108928 is 829801446.

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×644108928² = 829752622258618368, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 644108928.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2057700 + ... + 2058012.

It is an arithmetic number, because the mean of its divisors is an integer number (14052285).

Almost surely, 2^644108928 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 644108928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (899346240).

644108928 is an abundant number, since it is smaller than the sum of its proper divisors (1154583552).

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

644108928 is a wasteful number, since it uses less digits than its factorization.

644108928 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 586 (or 574 counting only the distinct ones).

The product of its (nonzero) digits is 110592, while the sum is 42.

The square root of 644108928 is about 25379.3011724121. The cubic root of 644108928 is about 863.6141967510.

The spelling of 644108928 in words is "six hundred forty-four million, one hundred eight thousand, nine hundred twenty-eight".