644702320 has 20 divisors (see below), whose sum is σ = 1498933080. Its totient is φ = 257880896.

The previous prime is 644702287. The next prime is 644702321. The reversal of 644702320 is 23207446.

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644702321) 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 3 ways as a sum of consecutive naturals, for example, 4029310 + ... + 4029469.

It is an arithmetic number, because the mean of its divisors is an integer number (74946654).

Almost surely, 2^644702320 is an apocalyptic number.

It is an amenable number.

644702320 is an abundant number, since it is smaller than the sum of its proper divisors (854230760).

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

644702320 is a wasteful number, since it uses less digits than its factorization.

644702320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8058792 (or 8058786 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 28.

The square root of 644702320 is about 25390.9889527761. The cubic root of 644702320 is about 863.8793198502.

Adding to 644702320 its reverse (23207446), we get a palindrome (667909766).

The spelling of 644702320 in words is "six hundred forty-four million, seven hundred two thousand, three hundred twenty".