28185309 has 6 divisors (see below), whose sum is σ = 40712126. Its totient is φ = 18790200.

The previous prime is 28185299. The next prime is 28185317. The reversal of 28185309 is 90358182.

It can be written as a sum of positive squares in only one way, i.e., 26163225 + 2022084 = 5115^2 + 1422^2 .

It is not a de Polignac number, because 28185309 - 2⁷ = 28185181 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 (28185319) 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, 1565842 + ... + 1565859.

Almost surely, 2^28185309 is an apocalyptic number.

It is an amenable number.

28185309 is a deficient number, since it is larger than the sum of its proper divisors (12526817).

28185309 is a wasteful number, since it uses less digits than its factorization.

28185309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3131707 (or 3131704 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 28185309 is about 5308.9838010678. The cubic root of 28185309 is about 304.3273143831.

The spelling of 28185309 in words is "twenty-eight million, one hundred eighty-five thousand, three hundred nine".