205411021 has 4 divisors (see below), whose sum is σ = 207719100. Its totient is φ = 203102944.

The previous prime is 205410971. The next prime is 205411027. The reversal of 205411021 is 120114502.

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 126450025 + 78960996 = 11245^2 + 8886^2 .

It is a cyclic number.

It is not a de Polignac number, because 205411021 - 2¹⁹ = 204886733 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 205410986 and 205411004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205411027) 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, 1153906 + ... + 1154083.

It is an arithmetic number, because the mean of its divisors is an integer number (51929775).

Almost surely, 2^205411021 is an apocalyptic number.

It is an amenable number.

205411021 is a deficient number, since it is larger than the sum of its proper divisors (2308079).

205411021 is an equidigital number, since it uses as much as digits as its factorization.

205411021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2308078.

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 205411021 is about 14332.1673517999. The cubic root of 205411021 is about 590.0306610514.

Adding to 205411021 its reverse (120114502), we get a palindrome (325525523).

The spelling of 205411021 in words is "two hundred five million, four hundred eleven thousand, twenty-one".