644641320 has 32 divisors (see below), whose sum is σ = 1933924320. Its totient is φ = 171904320.

The previous prime is 644641303. The next prime is 644641321. The reversal of 644641320 is 23146446.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is not an unprimeable number, because it can be changed into a prime (644641321) 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 7 ways as a sum of consecutive naturals, for example, 2685886 + ... + 2686125.

It is an arithmetic number, because the mean of its divisors is an integer number (60435135).

Almost surely, 2^644641320 is an apocalyptic number.

644641320 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644641320 is an abundant number, since it is smaller than the sum of its proper divisors (1289283000).

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

644641320 is a wasteful number, since it uses less digits than its factorization.

644641320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5372025 (or 5372021 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 30.

The square root of 644641320 is about 25389.7877108100. The cubic root of 644641320 is about 863.8520730114.

Adding to 644641320 its reverse (23146446), we get a palindrome (667787766).

The spelling of 644641320 in words is "six hundred forty-four million, six hundred forty-one thousand, three hundred twenty".