128328661 has 4 divisors (see below), whose sum is σ = 133908192. Its totient is φ = 122749132.

The previous prime is 128328649. The next prime is 128328701. The reversal of 128328661 is 166823821.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 128328661 - 2¹³ = 128320469 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 128328661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128328601) 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, 2789731 + ... + 2789776.

It is an arithmetic number, because the mean of its divisors is an integer number (33477048).

Almost surely, 2^128328661 is an apocalyptic number.

It is an amenable number.

128328661 is a deficient number, since it is larger than the sum of its proper divisors (5579531).

128328661 is an equidigital number, since it uses as much as digits as its factorization.

128328661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5579530.

The product of its digits is 27648, while the sum is 37.

The square root of 128328661 is about 11328.2240885321. The cubic root of 128328661 is about 504.3993918380.

The spelling of 128328661 in words is "one hundred twenty-eight million, three hundred twenty-eight thousand, six hundred sixty-one".