28135221 has 8 divisors (see below), whose sum is σ = 39720384. Its totient is φ = 17653440.

The previous prime is 28135193. The next prime is 28135231. The reversal of 28135221 is 12253182.

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

It is not a de Polignac number, because 28135221 - 2⁶ = 28135157 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 28135191 and 28135200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28135231) 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, 275785 + ... + 275886.

It is an arithmetic number, because the mean of its divisors is an integer number (4965048).

Almost surely, 2^28135221 is an apocalyptic number.

It is an amenable number.

28135221 is a deficient number, since it is larger than the sum of its proper divisors (11585163).

28135221 is a wasteful number, since it uses less digits than its factorization.

28135221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 551691.

The product of its digits is 960, while the sum is 24.

The square root of 28135221 is about 5304.2644164860. The cubic root of 28135221 is about 304.1469345386.

The spelling of 28135221 in words is "twenty-eight million, one hundred thirty-five thousand, two hundred twenty-one".