128536561 has 4 divisors (see below), whose sum is σ = 128560612. Its totient is φ = 128512512.

The previous prime is 128536553. The next prime is 128536621. The reversal of 128536561 is 165635821.

128536561 is a nontrivial binomial coefficient, being equal to C(16034, 2).

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 25310961 + 103225600 = 5031^2 + 10160^2 .

It is a 3-Lehmer number, since φ(128536561) divides (128536561-1)³.

It is a cyclic number.

It is not a de Polignac number, because 128536561 - 2³ = 128536553 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 128536561.

It is not an unprimeable number, because it can be changed into a prime (128536511) 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, 1 + ... + 16033.

It is an arithmetic number, because the mean of its divisors is an integer number (32140153).

It is a Poulet number, since it divides 2^128536560-1.

Almost surely, 2^128536561 is an apocalyptic number.

128536561 is the 16033-rd triangular number and also the 8017-th hexagonal number.

128536561 is the 5345-th centered nonagonal number.

It is an amenable number.

128536561 is a deficient number, since it is larger than the sum of its proper divisors (24051).

128536561 is an equidigital number, since it uses as much as digits as its factorization.

128536561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24050.

The product of its digits is 43200, while the sum is 37.

The square root of 128536561 is about 11337.3965706418. The cubic root of 128536561 is about 504.6716304652.

The spelling of 128536561 in words is "one hundred twenty-eight million, five hundred thirty-six thousand, five hundred sixty-one".