644130432 has 144 divisors (see below), whose sum is σ = 2037816690. Its totient is φ = 195148800.

The previous prime is 644130413. The next prime is 644130437. The reversal of 644130432 is 234031446.

644130432 is a `hidden beast` number, since 644 + 13 + 0 + 4 + 3 + 2 = 666.

It can be written as a sum of positive squares in only one way, i.e., 577152576 + 66977856 = 24024^2 + 8184^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is a junction number, because it is equal to n+sod(n) for n = 644130396 and 644130405.

It is not an unprimeable number, because it can be changed into a prime (644130437) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 137082 + ... + 141702.

Almost surely, 2^644130432 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 644130432, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1018908345).

644130432 is an abundant number, since it is smaller than the sum of its proper divisors (1393686258).

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

644130432 is a wasteful number, since it uses less digits than its factorization.

644130432 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4663 (or 4637 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 27.

The square root of 644130432 is about 25379.7248212032. The cubic root of 644130432 is about 863.6238074199.

Adding to 644130432 its reverse (234031446), we get a palindrome (878161878).

The spelling of 644130432 in words is "six hundred forty-four million, one hundred thirty thousand, four hundred thirty-two".