128505687 has 4 divisors (see below), whose sum is σ = 171340920. Its totient is φ = 85670456.

The previous prime is 128505679. The next prime is 128505733. The reversal of 128505687 is 786505821.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 786505821 = 3 ⋅262168607.

It is a cyclic number.

It is not a de Polignac number, because 128505687 - 2³ = 128505679 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128505677) 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 in 3 ways as a sum of consecutive naturals, for example, 21417612 + ... + 21417617.

It is an arithmetic number, because the mean of its divisors is an integer number (42835230).

Almost surely, 2^128505687 is an apocalyptic number.

128505687 is a deficient number, since it is larger than the sum of its proper divisors (42835233).

128505687 is an equidigital number, since it uses as much as digits as its factorization.

128505687 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42835232.

The product of its (nonzero) digits is 134400, while the sum is 42.

The square root of 128505687 is about 11336.0348887960. The cubic root of 128505687 is about 504.6312204852.

The spelling of 128505687 in words is "one hundred twenty-eight million, five hundred five thousand, six hundred eighty-seven".