28505 has 4 divisors (see below), whose sum is σ = 34212. Its totient is φ = 22800.

The previous prime is 28499. The next prime is 28513. The reversal of 28505 is 50582.

28505 = T₅₄ + T₅₅ + ... + T₆₈.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17689 + 10816 = 133^2 + 104^2 .

It is not a de Polignac number, because 28505 - 2¹⁰ = 27481 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2846 + ... + 2855.

It is an arithmetic number, because the mean of its divisors is an integer number (8553).

2²⁸⁵⁰⁵ is an apocalyptic number.

It is an amenable number.

28505 is a deficient number, since it is larger than the sum of its proper divisors (5707).

28505 is an equidigital number, since it uses as much as digits as its factorization.

28505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5706.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 28505 is about 168.8342382338. The cubic root of 28505 is about 30.5473599079.

The spelling of 28505 in words is "twenty-eight thousand, five hundred five".