644435389782 has 12 divisors (see below), whose sum is σ = 1396276677900. Its totient is φ = 214811796588.

The previous prime is 644435389781. The next prime is 644435389823. The reversal of 644435389782 is 287983534446.

644435389782 is a `hidden beast` number, since 6 + 4 + 4 + 4 + 3 + 538 + 97 + 8 + 2 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644435389781) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 17900983032 + ... + 17900983067.

It is an arithmetic number, because the mean of its divisors is an integer number (116356389825).

Almost surely, 2^644435389782 is an apocalyptic number.

644435389782 is an abundant number, since it is smaller than the sum of its proper divisors (751841288118).

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

644435389782 is a wasteful number, since it uses less digits than its factorization.

644435389782 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35801966107 (or 35801966104 counting only the distinct ones).

The product of its digits is 139345920, while the sum is 63.

The spelling of 644435389782 in words is "six hundred forty-four billion, four hundred thirty-five million, three hundred eighty-nine thousand, seven hundred eighty-two".