644513320 has 64 divisors (see below), whose sum is σ = 1597760640. Its totient is φ = 232032000.

The previous prime is 644513273. The next prime is 644513327. The reversal of 644513320 is 23315446.

644513320 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (644513327) 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, 37189 + ... + 51691.

It is an arithmetic number, because the mean of its divisors is an integer number (24965010).

Almost surely, 2^644513320 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 644513320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (798880320).

644513320 is an abundant number, since it is smaller than the sum of its proper divisors (953247320).

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

644513320 is a wasteful number, since it uses less digits than its factorization.

644513320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14626 (or 14622 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 28.

The square root of 644513320 is about 25387.2668871622. The cubic root of 644513320 is about 863.7948937288.

Adding to 644513320 its reverse (23315446), we get a palindrome (667828766).

The spelling of 644513320 in words is "six hundred forty-four million, five hundred thirteen thousand, three hundred twenty".