128520809 has 2 divisors, whose sum is σ = 128520810. Its totient is φ = 128520808.

The previous prime is 128520797. The next prime is 128520811. The reversal of 128520809 is 908025821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 110838784 + 17682025 = 10528^2 + 4205^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-128520809 is a prime.

Together with 128520811, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (128520409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64260404 + 64260405.

It is an arithmetic number, because the mean of its divisors is an integer number (64260405).

Almost surely, 2^128520809 is an apocalyptic number.

It is an amenable number.

128520809 is a deficient number, since it is larger than the sum of its proper divisors (1).

128520809 is an equidigital number, since it uses as much as digits as its factorization.

128520809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11520, while the sum is 35.

The square root of 128520809 is about 11336.7018572423. The cubic root of 128520809 is about 504.6510139905.

The spelling of 128520809 in words is "one hundred twenty-eight million, five hundred twenty thousand, eight hundred nine".