128289989 has 4 divisors (see below), whose sum is σ = 131757324. Its totient is φ = 124822656.

The previous prime is 128289983. The next prime is 128289991. The reversal of 128289989 is 989982821.

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 78021889 + 50268100 = 8833^2 + 7090^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-128289989 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128289983) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1733612 + ... + 1733685.

It is an arithmetic number, because the mean of its divisors is an integer number (32939331).

Almost surely, 2^128289989 is an apocalyptic number.

It is an amenable number.

128289989 is a deficient number, since it is larger than the sum of its proper divisors (3467335).

128289989 is an equidigital number, since it uses as much as digits as its factorization.

128289989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3467334.

The product of its digits is 1492992, while the sum is 56.

The square root of 128289989 is about 11326.5170727810. The cubic root of 128289989 is about 504.3487196217.

The spelling of 128289989 in words is "one hundred twenty-eight million, two hundred eighty-nine thousand, nine hundred eighty-nine".