686811819521 has 2 divisors, whose sum is σ = 686811819522. Its totient is φ = 686811819520.

The previous prime is 686811819469. The next prime is 686811819563. The reversal of 686811819521 is 125918118686.

686811819521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 401480640625 + 285331178896 = 633625^2 + 534164^2 .

It is a cyclic number.

It is not a de Polignac number, because 686811819521 - 2¹⁴ = 686811803137 is a prime.

It is not a weakly prime, because it can be changed into another prime (686811809521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343405909760 + 343405909761.

It is an arithmetic number, because the mean of its divisors is an integer number (343405909761).

Almost surely, 2^686811819521 is an apocalyptic number.

It is an amenable number.

686811819521 is a deficient number, since it is larger than the sum of its proper divisors (1).

686811819521 is an equidigital number, since it uses as much as digits as its factorization.

686811819521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1658880, while the sum is 56.

The spelling of 686811819521 in words is "six hundred eighty-six billion, eight hundred eleven million, eight hundred nineteen thousand, five hundred twenty-one".