644588064 has 192 divisors, whose sum is σ = 1983744000. Its totient is φ = 203233536.

The previous prime is 644588057. The next prime is 644588081. The reversal of 644588064 is 460885446.

644588064 is a `hidden beast` number, since 6 + 4 + 4 + 588 + 0 + 64 = 666.

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, 3239037 + ... + 3239235.

It is an arithmetic number, because the mean of its divisors is an integer number (10332000).

Almost surely, 2^644588064 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 644588064, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (991872000).

644588064 is an abundant number, since it is smaller than the sum of its proper divisors (1339155936).

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

644588064 is a wasteful number, since it uses less digits than its factorization.

644588064 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404 (or 390 counting only the distinct ones).

The product of its (nonzero) digits is 737280, while the sum is 45.

The square root of 644588064 is about 25388.7389210256. The cubic root of 644588064 is about 863.8282837756.

The spelling of 644588064 in words is "six hundred forty-four million, five hundred eighty-eight thousand, sixty-four".