644692608 has 384 divisors, whose sum is σ = 2288390400. Its totient is φ = 180278784.

The previous prime is 644692603. The next prime is 644692621. The reversal of 644692608 is 806296446.

It is a tau number, because it is divible by the number of its divisors (384).

It is not an unprimeable number, because it can be changed into a prime (644692603) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 13716841 + ... + 13716887.

It is an arithmetic number, because the mean of its divisors is an integer number (5959350).

Almost surely, 2^644692608 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 644692608, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1144195200).

644692608 is an abundant number, since it is smaller than the sum of its proper divisors (1643697792).

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

644692608 is an frugal number, since it uses more digits than its factorization.

644692608 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96 (or 59 counting only the distinct ones).

The product of its (nonzero) digits is 497664, while the sum is 45.

The square root of 644692608 is about 25390.7977031050. The cubic root of 644692608 is about 863.8749819111.

The spelling of 644692608 in words is "six hundred forty-four million, six hundred ninety-two thousand, six hundred eight".