128559661 has 4 divisors (see below), whose sum is σ = 136122012. Its totient is φ = 120997312.

The previous prime is 128559659. The next prime is 128559671. The reversal of 128559661 is 166955821.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166955821 = 673 ⋅248077.

It can be written as a sum of positive squares in 2 ways, for example, as 96138025 + 32421636 = 9805^2 + 5694^2 .

It is a cyclic number.

It is not a de Polignac number, because 128559661 - 2¹ = 128559659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128559611) 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, 3781150 + ... + 3781183.

It is an arithmetic number, because the mean of its divisors is an integer number (34030503).

Almost surely, 2^128559661 is an apocalyptic number.

It is an amenable number.

128559661 is a deficient number, since it is larger than the sum of its proper divisors (7562351).

128559661 is an equidigital number, since it uses as much as digits as its factorization.

128559661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7562350.

The product of its digits is 129600, while the sum is 43.

The square root of 128559661 is about 11338.4152772775. The cubic root of 128559661 is about 504.7018610763.

The spelling of 128559661 in words is "one hundred twenty-eight million, five hundred fifty-nine thousand, six hundred sixty-one".