128405509 has 4 divisors (see below), whose sum is σ = 129416704. Its totient is φ = 127394316.

The previous prime is 128405507. The next prime is 128405521. The reversal of 128405509 is 905504821.

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 128405509 - 2¹ = 128405507 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 (128405507) 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, 505407 + ... + 505660.

It is an arithmetic number, because the mean of its divisors is an integer number (32354176).

Almost surely, 2^128405509 is an apocalyptic number.

It is an amenable number.

128405509 is a deficient number, since it is larger than the sum of its proper divisors (1011195).

128405509 is a wasteful number, since it uses less digits than its factorization.

128405509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1011194.

The product of its (nonzero) digits is 14400, while the sum is 34.

The square root of 128405509 is about 11331.6154629426. The cubic root of 128405509 is about 504.5000561514.

The spelling of 128405509 in words is "one hundred twenty-eight million, four hundred five thousand, five hundred nine".