205561261 has 4 divisors (see below), whose sum is σ = 206182624. Its totient is φ = 204939900.

The previous prime is 205561241. The next prime is 205561289. The reversal of 205561261 is 162165502.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 205561261 - 2¹¹ = 205559213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205561201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 310185 + ... + 310846.

It is an arithmetic number, because the mean of its divisors is an integer number (51545656).

Almost surely, 2^205561261 is an apocalyptic number.

It is an amenable number.

205561261 is a deficient number, since it is larger than the sum of its proper divisors (621363).

205561261 is an equidigital number, since it uses as much as digits as its factorization.

205561261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 621362.

The product of its (nonzero) digits is 3600, while the sum is 28.

The square root of 205561261 is about 14337.4077503571. The cubic root of 205561261 is about 590.1744777473.

The spelling of 205561261 in words is "two hundred five million, five hundred sixty-one thousand, two hundred sixty-one".