644425320 has 256 divisors, whose sum is σ = 2438553600. Its totient is φ = 132341760.

The previous prime is 644425291. The next prime is 644425367. The reversal of 644425320 is 23524446.

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

It is an unprimeable number.

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 63 ways as a sum of consecutive naturals, for example, 895921 + ... + 896639.

It is an arithmetic number, because the mean of its divisors is an integer number (9525600).

Almost surely, 2^644425320 is an apocalyptic number.

644425320 is a gapful number since it is divisible by the number (60) 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 644425320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1219276800).

644425320 is an abundant number, since it is smaller than the sum of its proper divisors (1794128280).

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

644425320 is a wasteful number, since it uses less digits than its factorization.

644425320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 848 (or 844 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 30.

The square root of 644425320 is about 25385.5336756981. The cubic root of 644425320 is about 863.7555785804.

Adding to 644425320 its reverse (23524446), we get a palindrome (667949766).

The spelling of 644425320 in words is "six hundred forty-four million, four hundred twenty-five thousand, three hundred twenty".