28909291 has 4 divisors (see below), whose sum is σ = 28921752. Its totient is φ = 28896832.

The previous prime is 28909273. The next prime is 28909297. The reversal of 28909291 is 19290982.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 19290982 = 2 ⋅9645491.

It is a cyclic number.

It is not a de Polignac number, because 28909291 - 2⁹ = 28908779 is a prime.

It is a super-2 number, since 2×28909291² = 1671494212245362, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28909297) 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, 1606 + ... + 7771.

It is an arithmetic number, because the mean of its divisors is an integer number (7230438).

Almost surely, 2^28909291 is an apocalyptic number.

28909291 is a deficient number, since it is larger than the sum of its proper divisors (12461).

28909291 is an equidigital number, since it uses as much as digits as its factorization.

28909291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12460.

The product of its (nonzero) digits is 23328, while the sum is 40.

The square root of 28909291 is about 5376.7360917196. The cubic root of 28909291 is about 306.9110183608.

The spelling of 28909291 in words is "twenty-eight million, nine hundred nine thousand, two hundred ninety-one".