205581 has 16 divisors (see below), whose sum is σ = 302400. Its totient is φ = 123648.

The previous prime is 205559. The next prime is 205589. The reversal of 205581 is 185502.

It is not a de Polignac number, because 205581 - 2⁵ = 205549 is a prime.

It is a super-2 number, since 2×205581² = 84527095122, which contains 22 as substring.

205581 is a lucky number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 205581.

It is not an unprimeable number, because it can be changed into a prime (205589) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1410 + ... + 1548.

It is an arithmetic number, because the mean of its divisors is an integer number (18900).

2²⁰⁵⁵⁸¹ is an apocalyptic number.

It is an amenable number.

205581 is a deficient number, since it is larger than the sum of its proper divisors (96819).

205581 is a wasteful number, since it uses less digits than its factorization.

205581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188.

The product of its (nonzero) digits is 400, while the sum is 21.

The square root of 205581 is about 453.4104101143. The cubic root of 205581 is about 59.0193367625.

The spelling of 205581 in words is "two hundred five thousand, five hundred eighty-one".