128642209 has 2 divisors, whose sum is σ = 128642210. Its totient is φ = 128642208.

The previous prime is 128642207. The next prime is 128642221. The reversal of 128642209 is 902246821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 97950609 + 30691600 = 9897^2 + 5540^2 .

It is a cyclic number.

It is not a de Polignac number, because 128642209 - 2¹ = 128642207 is a prime.

Together with 128642207, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (128642201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64321104 + 64321105.

It is an arithmetic number, because the mean of its divisors is an integer number (64321105).

Almost surely, 2^128642209 is an apocalyptic number.

It is an amenable number.

128642209 is a deficient number, since it is larger than the sum of its proper divisors (1).

128642209 is an equidigital number, since it uses as much as digits as its factorization.

128642209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 128642209 is about 11342.0548843673. The cubic root of 128642209 is about 504.8098607786.

The spelling of 128642209 in words is "one hundred twenty-eight million, six hundred forty-two thousand, two hundred nine".