205605561 has 16 divisors (see below), whose sum is σ = 314121600. Its totient is φ = 117182208.

The previous prime is 205605523. The next prime is 205605581. The reversal of 205605561 is 165506502.

It is a de Polignac number, because none of the positive numbers 2^k-205605561 is a prime.

It is not an unprimeable number, because it can be changed into a prime (205605581) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4416 + ... + 20753.

It is an arithmetic number, because the mean of its divisors is an integer number (19632600).

Almost surely, 2^205605561 is an apocalyptic number.

205605561 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

205605561 is a deficient number, since it is larger than the sum of its proper divisors (108516039).

205605561 is a wasteful number, since it uses less digits than its factorization.

205605561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25568.

The product of its (nonzero) digits is 9000, while the sum is 30.

The square root of 205605561 is about 14338.9525768098. The cubic root of 205605561 is about 590.2168703838.

The spelling of 205605561 in words is "two hundred five million, six hundred five thousand, five hundred sixty-one".