644500664745 has 32 divisors (see below), whose sum is σ = 1210367278848. Its totient is φ = 286665931008.

The previous prime is 644500664741. The next prime is 644500664771. The reversal of 644500664745 is 547466005446.

It is not a de Polignac number, because 644500664745 - 2² = 644500664741 is a prime.

It is a super-2 number, since 2×644500664745² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644500664741) 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, 82943434 + ... + 82951203.

It is an arithmetic number, because the mean of its divisors is an integer number (37823977464).

Almost surely, 2^644500664745 is an apocalyptic number.

It is an amenable number.

644500664745 is a deficient number, since it is larger than the sum of its proper divisors (565866614103).

644500664745 is a wasteful number, since it uses less digits than its factorization.

644500664745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165894689.

The product of its (nonzero) digits is 9676800, while the sum is 51.

The spelling of 644500664745 in words is "six hundred forty-four billion, five hundred million, six hundred sixty-four thousand, seven hundred forty-five".