205431021 has 36 divisors (see below), whose sum is σ = 319349628. Its totient is φ = 127191168.

The previous prime is 205431011. The next prime is 205431049. The reversal of 205431021 is 120134502.

205431021 is a `hidden beast` number, since 20 + 543 + 102 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 127373796 + 78057225 = 11286^2 + 8835^2 .

It is not a de Polignac number, because 205431021 - 2¹⁵ = 205398253 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 205430985 and 205431003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205431001) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 171601 + ... + 172793.

It is an arithmetic number, because the mean of its divisors is an integer number (8870823).

Almost surely, 2^205431021 is an apocalyptic number.

It is an amenable number.

205431021 is a deficient number, since it is larger than the sum of its proper divisors (113918607).

205431021 is a wasteful number, since it uses less digits than its factorization.

205431021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1290 (or 1268 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 205431021 is about 14332.8650659943. The cubic root of 205431021 is about 590.0498100244.

Adding to 205431021 its reverse (120134502), we get a palindrome (325565523).

The spelling of 205431021 in words is "two hundred five million, four hundred thirty-one thousand, twenty-one".