685128517 has 4 divisors (see below), whose sum is σ = 687317740. Its totient is φ = 682939296.

The previous prime is 685128511. The next prime is 685128553. The reversal of 685128517 is 715821586.

685128517 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 80263681 + 604864836 = 8959^2 + 24594^2 .

It is a cyclic number.

It is not a de Polignac number, because 685128517 - 2²³ = 676739909 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (685128511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1094142 + ... + 1094767.

It is an arithmetic number, because the mean of its divisors is an integer number (171829435).

Almost surely, 2^685128517 is an apocalyptic number.

It is an amenable number.

685128517 is a deficient number, since it is larger than the sum of its proper divisors (2189223).

685128517 is a wasteful number, since it uses less digits than its factorization.

685128517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2189222.

The product of its digits is 134400, while the sum is 43.

The square root of 685128517 is about 26174.9597325383. The cubic root of 685128517 is about 881.5711073533.

The spelling of 685128517 in words is "six hundred eighty-five million, one hundred twenty-eight thousand, five hundred seventeen".