644606512456 has 8 divisors (see below), whose sum is σ = 1208637210870. Its totient is φ = 322303256224.

The previous prime is 644606512427. The next prime is 644606512457. The reversal of 644606512456 is 654215606446.

It can be written as a sum of positive squares in only one way, i.e., 625785416356 + 18821096100 = 791066^2 + 137190^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (644606512457) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40287907021 + ... + 40287907036.

Almost surely, 2^644606512456 is an apocalyptic number.

It is an amenable number.

644606512456 is a deficient number, since it is larger than the sum of its proper divisors (564030698414).

644606512456 is a wasteful number, since it uses less digits than its factorization.

644606512456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80575814063 (or 80575814059 counting only the distinct ones).

The product of its (nonzero) digits is 4147200, while the sum is 49.

The spelling of 644606512456 in words is "six hundred forty-four billion, six hundred six million, five hundred twelve thousand, four hundred fifty-six".