128688517 has 4 divisors (see below), whose sum is σ = 128826796. Its totient is φ = 128550240.

The previous prime is 128688503. The next prime is 128688523. The reversal of 128688517 is 715886821.

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 71927361 + 56761156 = 8481^2 + 7534^2 .

It is a cyclic number.

It is not a de Polignac number, because 128688517 - 2¹¹ = 128686469 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 (128688817) 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, 67734 + ... + 69607.

It is an arithmetic number, because the mean of its divisors is an integer number (32206699).

Almost surely, 2^128688517 is an apocalyptic number.

It is an amenable number.

128688517 is a deficient number, since it is larger than the sum of its proper divisors (138279).

128688517 is an equidigital number, since it uses as much as digits as its factorization.

128688517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138278.

The product of its digits is 215040, while the sum is 46.

The square root of 128688517 is about 11344.0961297055. The cubic root of 128688517 is about 504.8704265156.

The spelling of 128688517 in words is "one hundred twenty-eight million, six hundred eighty-eight thousand, five hundred seventeen".