644716776651 has 16 divisors (see below), whose sum is σ = 917610243840. Its totient is φ = 401454476640.

The previous prime is 644716776647. The next prime is 644716776653. The reversal of 644716776651 is 156677617446.

It is not a de Polignac number, because 644716776651 - 2² = 644716776647 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644716776653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 79649620 + ... + 79657713.

It is an arithmetic number, because the mean of its divisors is an integer number (57350640240).

Almost surely, 2^644716776651 is an apocalyptic number.

644716776651 is a deficient number, since it is larger than the sum of its proper divisors (272893467189).

644716776651 is a wasteful number, since it uses less digits than its factorization.

644716776651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159307426.

The product of its digits is 35562240, while the sum is 60.

The spelling of 644716776651 in words is "six hundred forty-four billion, seven hundred sixteen million, seven hundred seventy-six thousand, six hundred fifty-one".