28561 has 5 divisors (see below), whose sum is σ = 30941. Its totient is φ = 26364.

The previous prime is 28559. The next prime is 28571. The reversal of 28561 is 16582.

28561 = T₁₆₈ + T₁₆₉.

28561 = 119² + 120².

It is a happy number.

The square root of 28561 is 169.

It is a perfect power (a square, a biquadrate), and thus also a powerful number.

28561 is nontrivially palindromic in base 12.

It can be written as a sum of positive squares in 2 ways, for example, as 14161 + 14400 = 119^2 + 120^2 .

It is not a de Polignac number, because 28561 - 2¹ = 28559 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (28541) by changing a digit.

It is a polite number, since it can be written in 4 ways as a sum of consecutive naturals, for example, 2191 + ... + 2203.

28561 is a Friedman number, since it can be written as (8+5)^(6*1-2), using all its digits and the basic arithmetic operations.

2²⁸⁵⁶¹ is an apocalyptic number.

28561 is the 169-th square number.

28561 is the 120-th centered square number and also the 85-th centered octagonal number.

It is an amenable number.

28561 is a deficient number, since it is larger than the sum of its proper divisors (2380).

28561 is an frugal number, since it uses more digits than its factorization.

28561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52 (or 13 counting only the distinct ones).

The product of its digits is 480, while the sum is 22.

The cubic root of 28561 is about 30.5673509404.

The spelling of 28561 in words is "twenty-eight thousand, five hundred sixty-one".