644593664 has 192 divisors, whose sum is σ = 1585059840. Its totient is φ = 258048000.

The previous prime is 644593661. The next prime is 644593679. The reversal of 644593664 is 466395446.

Its product of digits (1866240) is a multiple of the sum of its prime divisors (128).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644593661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9078749 + ... + 9078819.

It is an arithmetic number, because the mean of its divisors is an integer number (8255520).

Almost surely, 2^644593664 is an apocalyptic number.

644593664 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644593664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (792529920).

644593664 is an abundant number, since it is smaller than the sum of its proper divisors (940466176).

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

644593664 is a wasteful number, since it uses less digits than its factorization.

644593664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 148 (or 128 counting only the distinct ones).

The product of its digits is 1866240, while the sum is 47.

The square root of 644593664 is about 25388.8492059014. The cubic root of 644593664 is about 863.8307853342.

The spelling of 644593664 in words is "six hundred forty-four million, five hundred ninety-three thousand, six hundred sixty-four".