28138209 has 8 divisors (see below), whose sum is σ = 40928352. Its totient is φ = 17053440.

The previous prime is 28138199. The next prime is 28138217. The reversal of 28138209 is 90283182.

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

It is not a de Polignac number, because 28138209 - 2⁴ = 28138193 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33), and also a Moran number because the ratio is a prime number: 852673 = 28138209 / (2 + 8 + 1 + 3 + 8 + 2 + 0 + 9).

It is a self number, because there is not a number n which added to its sum of digits gives 28138209.

It is not an unprimeable number, because it can be changed into a prime (28138709) 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, 426304 + ... + 426369.

It is an arithmetic number, because the mean of its divisors is an integer number (5116044).

Almost surely, 2^28138209 is an apocalyptic number.

It is an amenable number.

28138209 is a deficient number, since it is larger than the sum of its proper divisors (12790143).

28138209 is a wasteful number, since it uses less digits than its factorization.

28138209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 852687.

The product of its (nonzero) digits is 6912, while the sum is 33.

The square root of 28138209 is about 5304.5460691750. The cubic root of 28138209 is about 304.1577011014.

The spelling of 28138209 in words is "twenty-eight million, one hundred thirty-eight thousand, two hundred nine".