644651665765365 has 16 divisors (see below), whose sum is σ = 1050903847588608. Its totient is φ = 337327160953536.

The previous prime is 644651665765363. The next prime is 644651665765409. The reversal of 644651665765365 is 563567566156446.

It is not a de Polignac number, because 644651665765365 - 2¹ = 644651665765363 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644651665765363) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 405441298429 + ... + 405441300018.

It is an arithmetic number, because the mean of its divisors is an integer number (65681490474288).

Almost surely, 2^{644651665765365} is an apocalyptic number.

It is an amenable number.

644651665765365 is a deficient number, since it is larger than the sum of its proper divisors (406252181823243).

644651665765365 is a wasteful number, since it uses less digits than its factorization.

644651665765365 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 810882598508.

The product of its digits is 9797760000, while the sum is 75.

The spelling of 644651665765365 in words is "six hundred forty-four trillion, six hundred fifty-one billion, six hundred sixty-five million, seven hundred sixty-five thousand, three hundred sixty-five".