206581 has 4 divisors (see below), whose sum is σ = 207532. Its totient is φ = 205632.

The previous prime is 206551. The next prime is 206593. The reversal of 206581 is 185602.

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: 185602 = 2 ⋅92801.

It can be written as a sum of positive squares in 2 ways, for example, as 18225 + 188356 = 135^2 + 434^2 .

It is a cyclic number.

It is not a de Polignac number, because 206581 - 2⁹ = 206069 is a prime.

It is a super-2 number, since 2×206581² = 85351419122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (206501) 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, 31 + ... + 643.

It is an arithmetic number, because the mean of its divisors is an integer number (51883).

2²⁰⁶⁵⁸¹ is an apocalyptic number.

It is an amenable number.

206581 is a deficient number, since it is larger than the sum of its proper divisors (951).

206581 is an equidigital number, since it uses as much as digits as its factorization.

206581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 950.

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

The square root of 206581 is about 454.5118260288. The cubic root of 206581 is about 59.1148772053.

It can be divided in two parts, 206 and 581, that added together give a palindrome (787).

The spelling of 206581 in words is "two hundred six thousand, five hundred eighty-one".