128398861 has 2 divisors, whose sum is σ = 128398862. Its totient is φ = 128398860.

The previous prime is 128398859. The next prime is 128398871. The reversal of 128398861 is 168893821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 124322500 + 4076361 = 11150^2 + 2019^2 .

It is an emirp because it is prime and its reverse (168893821) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 128398861 - 2¹ = 128398859 is a prime.

Together with 128398859, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128398871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64199430 + 64199431.

It is an arithmetic number, because the mean of its divisors is an integer number (64199431).

Almost surely, 2^128398861 is an apocalyptic number.

It is an amenable number.

128398861 is a deficient number, since it is larger than the sum of its proper divisors (1).

128398861 is an equidigital number, since it uses as much as digits as its factorization.

128398861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 165888, while the sum is 46.

The square root of 128398861 is about 11331.3221205647. The cubic root of 128398861 is about 504.4913494267.

The spelling of 128398861 in words is "one hundred twenty-eight million, three hundred ninety-eight thousand, eight hundred sixty-one".