644727216677 has 2 divisors, whose sum is σ = 644727216678. Its totient is φ = 644727216676.

The previous prime is 644727216589. The next prime is 644727216701. The reversal of 644727216677 is 776612727446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 537268476196 + 107458740481 = 732986^2 + 327809^2 .

It is a cyclic number.

It is not a de Polignac number, because 644727216677 - 2¹² = 644727212581 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644727216877) 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 as a sum of consecutive naturals, namely, 322363608338 + 322363608339.

It is an arithmetic number, because the mean of its divisors is an integer number (322363608339).

Almost surely, 2^644727216677 is an apocalyptic number.

It is an amenable number.

644727216677 is a deficient number, since it is larger than the sum of its proper divisors (1).

644727216677 is an equidigital number, since it uses as much as digits as its factorization.

644727216677 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 33191424, while the sum is 59.

The spelling of 644727216677 in words is "six hundred forty-four billion, seven hundred twenty-seven million, two hundred sixteen thousand, six hundred seventy-seven".