687777365521 has 2 divisors, whose sum is σ = 687777365522. Its totient is φ = 687777365520.

The previous prime is 687777365501. The next prime is 687777365551. The reversal of 687777365521 is 125563777786.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 474495034896 + 213282330625 = 688836^2 + 461825^2 .

It is a cyclic number.

It is not a de Polignac number, because 687777365521 - 2¹⁷ = 687777234449 is a prime.

It is not a weakly prime, because it can be changed into another prime (687777365501) by changing a digit.

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 as a sum of consecutive naturals, namely, 343888682760 + 343888682761.

It is an arithmetic number, because the mean of its divisors is an integer number (343888682761).

Almost surely, 2^687777365521 is an apocalyptic number.

It is an amenable number.

687777365521 is a deficient number, since it is larger than the sum of its proper divisors (1).

687777365521 is an equidigital number, since it uses as much as digits as its factorization.

687777365521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 103723200, while the sum is 64.

The spelling of 687777365521 in words is "six hundred eighty-seven billion, seven hundred seventy-seven million, three hundred sixty-five thousand, five hundred twenty-one".