20128809 has 8 divisors (see below), whose sum is σ = 28251040. Its totient is φ = 12712896.

The previous prime is 20128793. The next prime is 20128837. The reversal of 20128809 is 90882102.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20128809 - 2⁴ = 20128793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20128879) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 176512 + ... + 176625.

It is an arithmetic number, because the mean of its divisors is an integer number (3531380).

Almost surely, 2^20128809 is an apocalyptic number.

It is an amenable number.

20128809 is a deficient number, since it is larger than the sum of its proper divisors (8122231).

20128809 is a wasteful number, since it uses less digits than its factorization.

20128809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 353159.

The product of its (nonzero) digits is 2304, while the sum is 30.

The square root of 20128809 is about 4486.5141256882. The cubic root of 20128809 is about 272.0232507878.

The spelling of 20128809 in words is "twenty million, one hundred twenty-eight thousand, eight hundred nine".