128609 has 6 divisors (see below), whose sum is σ = 139446. Its totient is φ = 118560.

The previous prime is 128603. The next prime is 128621. The reversal of 128609 is 906821.

It can be written as a sum of positive squares in 3 ways, for example, as 16384 + 112225 = 128^2 + 335^2 .

It is not a de Polignac number, because 128609 - 2¹² = 124513 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 (128603) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 212 + ... + 549.

It is an arithmetic number, because the mean of its divisors is an integer number (23241).

2¹²⁸⁶⁰⁹ is an apocalyptic number.

It is an amenable number.

128609 is a deficient number, since it is larger than the sum of its proper divisors (10837).

128609 is an equidigital number, since it uses as much as digits as its factorization.

128609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 787 (or 774 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 128609 is about 358.6209698275. The cubic root of 128609 is about 50.4766418134.

It can be divided in two parts, 128 and 609, that added together give a palindrome (737).

The spelling of 128609 in words is "one hundred twenty-eight thousand, six hundred nine".