644617128 has 64 divisors (see below), whose sum is σ = 1653220800. Its totient is φ = 209341440.

The previous prime is 644617081. The next prime is 644617139. The reversal of 644617128 is 821716446.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 731248 + ... + 732128.

It is an arithmetic number, because the mean of its divisors is an integer number (25831575).

Almost surely, 2^644617128 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 644617128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (826610400).

644617128 is an abundant number, since it is smaller than the sum of its proper divisors (1008603672).

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

644617128 is a wasteful number, since it uses less digits than its factorization.

644617128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1642 (or 1638 counting only the distinct ones).

The product of its digits is 64512, while the sum is 39.

The square root of 644617128 is about 25389.3112943223. The cubic root of 644617128 is about 863.8412667071.

The spelling of 644617128 in words is "six hundred forty-four million, six hundred seventeen thousand, one hundred twenty-eight".