205621 has 4 divisors (see below), whose sum is σ = 221452. Its totient is φ = 189792.

The previous prime is 205619. The next prime is 205627. The reversal of 205621 is 126502.

It is a happy number.

205621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 108900 + 96721 = 330^2 + 311^2 .

It is a cyclic number.

It is not a de Polignac number, because 205621 - 2¹ = 205619 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 205595 and 205604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205627) 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, 7896 + ... + 7921.

It is an arithmetic number, because the mean of its divisors is an integer number (55363).

2²⁰⁵⁶²¹ is an apocalyptic number.

It is an amenable number.

205621 is a deficient number, since it is larger than the sum of its proper divisors (15831).

205621 is a wasteful number, since it uses less digits than its factorization.

205621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15830.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 205621 is about 453.4545181162. The cubic root of 205621 is about 59.0231643217.

The spelling of 205621 in words is "two hundred five thousand, six hundred twenty-one".