644756376 has 128 divisors (see below), whose sum is σ = 1822176000. Its totient is φ = 188398080.

The previous prime is 644756363. The next prime is 644756377. The reversal of 644756376 is 673657446.

644756376 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644756377) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1455211 + ... + 1455653.

It is an arithmetic number, because the mean of its divisors is an integer number (14235750).

Almost surely, 2^644756376 is an apocalyptic number.

644756376 is a gapful number since it is divisible by the number (66) 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 644756376, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (911088000).

644756376 is an abundant number, since it is smaller than the sum of its proper divisors (1177419624).

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

644756376 is a wasteful number, since it uses less digits than its factorization.

644756376 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 649 (or 645 counting only the distinct ones).

The product of its digits is 2540160, while the sum is 48.

The square root of 644756376 is about 25392.0534025903. The cubic root of 644756376 is about 863.9034635798.

The spelling of 644756376 in words is "six hundred forty-four million, seven hundred fifty-six thousand, three hundred seventy-six".