128509 has 2 divisors, whose sum is σ = 128510. Its totient is φ = 128508.

The previous prime is 128489. The next prime is 128519. The reversal of 128509 is 905821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 120409 + 8100 = 347^2 + 90^2 .

It is a cyclic number.

It is not a de Polignac number, because 128509 - 2⁵ = 128477 is a prime.

It is an Ulam number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64254 + 64255.

It is an arithmetic number, because the mean of its divisors is an integer number (64255).

2¹²⁸⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

128509 is a deficient number, since it is larger than the sum of its proper divisors (1).

128509 is an equidigital number, since it uses as much as digits as its factorization.

128509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 128509 is about 358.4815197468. The cubic root of 128509 is about 50.4635557074.

The spelling of 128509 in words is "one hundred twenty-eight thousand, five hundred nine".