128779309 has 4 divisors (see below), whose sum is σ = 128812860. Its totient is φ = 128745760.

The previous prime is 128779307. The next prime is 128779327. The reversal of 128779309 is 903977821.

It is a happy number.

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 71064900 + 57714409 = 8430^2 + 7597^2 .

It is a cyclic number.

It is not a de Polignac number, because 128779309 - 2¹ = 128779307 is a prime.

It is a super-2 number, since 2×128779309² = 33168220853034962, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128779307) 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 in 3 ways as a sum of consecutive naturals, for example, 10144 + ... + 18985.

It is an arithmetic number, because the mean of its divisors is an integer number (32203215).

Almost surely, 2^128779309 is an apocalyptic number.

It is an amenable number.

128779309 is a deficient number, since it is larger than the sum of its proper divisors (33551).

128779309 is an equidigital number, since it uses as much as digits as its factorization.

128779309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33550.

The product of its (nonzero) digits is 190512, while the sum is 46.

The square root of 128779309 is about 11348.0971532676. The cubic root of 128779309 is about 504.9891302434.

Adding to 128779309 its product of nonzero digits (190512), we get a palindrome (128969821).

The spelling of 128779309 in words is "one hundred twenty-eight million, seven hundred seventy-nine thousand, three hundred nine".