128766809 has 2 divisors, whose sum is σ = 128766810. Its totient is φ = 128766808.

The previous prime is 128766797. The next prime is 128766871. The reversal of 128766809 is 908667821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 108264025 + 20502784 = 10405^2 + 4528^2 .

It is an emirp because it is prime and its reverse (908667821) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 128766809 - 2¹⁶ = 128701273 is a prime.

It is a super-2 number, since 2×128766809² = 33161782200084962, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (128766889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64383404 + 64383405.

It is an arithmetic number, because the mean of its divisors is an integer number (64383405).

Almost surely, 2^128766809 is an apocalyptic number.

It is an amenable number.

128766809 is a deficient number, since it is larger than the sum of its proper divisors (1).

128766809 is an equidigital number, since it uses as much as digits as its factorization.

128766809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 290304, while the sum is 47.

The square root of 128766809 is about 11347.5463867745. The cubic root of 128766809 is about 504.9727907439.

The spelling of 128766809 in words is "one hundred twenty-eight million, seven hundred sixty-six thousand, eight hundred nine".