644992277645 has 4 divisors (see below), whose sum is σ = 773990733180. Its totient is φ = 515993822112.

The previous prime is 644992277597. The next prime is 644992277653. The reversal of 644992277645 is 546772299446.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 215833647241 + 429158630404 = 464579^2 + 655102^2 .

It is a cyclic number.

It is not a de Polignac number, because 644992277645 - 2⁶ = 644992277581 is a prime.

It is a super-3 number, since 3×644992277645³ (a number of 36 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

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 in 3 ways as a sum of consecutive naturals, for example, 64499227760 + ... + 64499227769.

It is an arithmetic number, because the mean of its divisors is an integer number (193497683295).

Almost surely, 2^644992277645 is an apocalyptic number.

It is an amenable number.

644992277645 is a deficient number, since it is larger than the sum of its proper divisors (128998455535).

644992277645 is a wasteful number, since it uses less digits than its factorization.

644992277645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128998455534.

The product of its digits is 182891520, while the sum is 65.

The spelling of 644992277645 in words is "six hundred forty-four billion, nine hundred ninety-two million, two hundred seventy-seven thousand, six hundred forty-five".