205021 has 4 divisors (see below), whose sum is σ = 208444. Its totient is φ = 201600.

The previous prime is 205019. The next prime is 205031. The reversal of 205021 is 120502.

205021 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, and also an emirpimes, since its reverse is a distinct semiprime: 120502 = 2 ⋅60251.

It can be written as a sum of positive squares in 2 ways, for example, as 68121 + 136900 = 261^2 + 370^2 .

It is a cyclic number.

It is not a de Polignac number, because 205021 - 2¹ = 205019 is a prime.

It is a super-2 number, since 2×205021² = 84067220882, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 204989 and 205007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205031) 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, 1620 + ... + 1741.

It is an arithmetic number, because the mean of its divisors is an integer number (52111).

2²⁰⁵⁰²¹ is an apocalyptic number.

It is an amenable number.

205021 is a deficient number, since it is larger than the sum of its proper divisors (3423).

205021 is an equidigital number, since it uses as much as digits as its factorization.

205021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3422.

The product of its (nonzero) digits is 20, while the sum is 10.

The square root of 205021 is about 452.7924469335. The cubic root of 205021 is about 58.9656987251.

Adding to 205021 its reverse (120502), we get a palindrome (325523).

It can be divided in two parts, 20502 and 1, that added together give a triangular number (20503 = T₂₀₂).

The spelling of 205021 in words is "two hundred five thousand, twenty-one".