644576538664 has 16 divisors (see below), whose sum is σ = 1212232317120. Its totient is φ = 321314587440.

The previous prime is 644576538583. The next prime is 644576538667. The reversal of 644576538664 is 466835675446.

It is a junction number, because it is equal to n+sod(n) for n = 644576538596 and 644576538605.

It is not an unprimeable number, because it can be changed into a prime (644576538667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 121707424 + ... + 121712719.

It is an arithmetic number, because the mean of its divisors is an integer number (75764519820).

Almost surely, 2^644576538664 is an apocalyptic number.

It is an amenable number.

644576538664 is a deficient number, since it is larger than the sum of its proper divisors (567655778456).

644576538664 is a wasteful number, since it uses less digits than its factorization.

644576538664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 243420480 (or 243420476 counting only the distinct ones).

The product of its digits is 348364800, while the sum is 64.

The spelling of 644576538664 in words is "six hundred forty-four billion, five hundred seventy-six million, five hundred thirty-eight thousand, six hundred sixty-four".