644040884 has 6 divisors (see below), whose sum is σ = 1127071554. Its totient is φ = 322020440.

The previous prime is 644040883. The next prime is 644040913. The reversal of 644040884 is 488040446.

It can be written as a sum of positive squares in only one way, i.e., 643738384 + 302500 = 25372^2 + 550^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644040883) 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 as a sum of consecutive naturals, namely, 80505107 + ... + 80505114.

It is an arithmetic number, because the mean of its divisors is an integer number (187845259).

Almost surely, 2^644040884 is an apocalyptic number.

It is an amenable number.

644040884 is a deficient number, since it is larger than the sum of its proper divisors (483030670).

644040884 is a wasteful number, since it uses less digits than its factorization.

644040884 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161010225 (or 161010223 counting only the distinct ones).

The product of its (nonzero) digits is 98304, while the sum is 38.

The square root of 644040884 is about 25377.9605957610. The cubic root of 644040884 is about 863.5837847967.

The spelling of 644040884 in words is "six hundred forty-four million, forty thousand, eight hundred eighty-four".