28309505 has 32 divisors (see below), whose sum is σ = 41990400. Its totient is φ = 18251520.

The previous prime is 28309499. The next prime is 28309507. The reversal of 28309505 is 50590382.

It is a happy number.

It is not a de Polignac number, because 28309505 - 2²⁰ = 27260929 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (28309507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 28670 + ... + 29640.

It is an arithmetic number, because the mean of its divisors is an integer number (1312200).

Almost surely, 2^28309505 is an apocalyptic number.

It is an amenable number.

28309505 is a deficient number, since it is larger than the sum of its proper divisors (13680895).

28309505 is an equidigital number, since it uses as much as digits as its factorization.

28309505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1014 (or 1000 counting only the distinct ones).

The product of its (nonzero) digits is 10800, while the sum is 32.

The square root of 28309505 is about 5320.6677212545. The cubic root of 28309505 is about 304.7736563103.

Adding to 28309505 its reverse (50590382), we get a palindrome (78899887).

The spelling of 28309505 in words is "twenty-eight million, three hundred nine thousand, five hundred five".