28531 has 4 divisors (see below), whose sum is σ = 28912. Its totient is φ = 28152.

The previous prime is 28517. The next prime is 28537. The reversal of 28531 is 13582.

It is a happy number.

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: 13582 = 2 ⋅6791.

It is a cyclic number.

It is not a de Polignac number, because 28531 - 2⁵ = 28499 is a prime.

It is a super-2 number, since 2×28531² = 1628035922, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 28499 and 28508.

It is not an unprimeable number, because it can be changed into a prime (28537) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36 + ... + 241.

It is an arithmetic number, because the mean of its divisors is an integer number (7228).

2²⁸⁵³¹ is an apocalyptic number.

28531 is a deficient number, since it is larger than the sum of its proper divisors (381).

28531 is a wasteful number, since it uses less digits than its factorization.

28531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 380.

The product of its digits is 240, while the sum is 19.

The square root of 28531 is about 168.9112192840. The cubic root of 28531 is about 30.5566447117.

The spelling of 28531 in words is "twenty-eight thousand, five hundred thirty-one".