205531 has 4 divisors (see below), whose sum is σ = 209952. Its totient is φ = 201112.

The previous prime is 205529. The next prime is 205537. The reversal of 205531 is 135502.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 135502 = 2 ⋅67751.

It is a cyclic number.

It is not a de Polignac number, because 205531 - 2¹ = 205529 is a prime.

It is a super-2 number, since 2×205531² = 84485983922, which contains 22 as substring.

It is a Duffinian number.

205531 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (205537) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2140 + ... + 2233.

It is an arithmetic number, because the mean of its divisors is an integer number (52488).

2²⁰⁵⁵³¹ is an apocalyptic number.

205531 is a deficient number, since it is larger than the sum of its proper divisors (4421).

205531 is an equidigital number, since it uses as much as digits as its factorization.

205531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4420.

The product of its (nonzero) digits is 150, while the sum is 16.

The square root of 205531 is about 453.3552690771. The cubic root of 205531 is about 59.0145516152.

The spelling of 205531 in words is "two hundred five thousand, five hundred thirty-one".