205561 has 8 divisors (see below), whose sum is σ = 224000. Its totient is φ = 187920.

The previous prime is 205559. The next prime is 205589. The reversal of 205561 is 165502.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 205561 - 2¹ = 205559 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 415 + ... + 763.

It is an arithmetic number, because the mean of its divisors is an integer number (28000).

2²⁰⁵⁵⁶¹ is an apocalyptic number.

It is an amenable number.

205561 is a deficient number, since it is larger than the sum of its proper divisors (18439).

205561 is a wasteful number, since it uses less digits than its factorization.

205561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 399.

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 205561 is about 453.3883545042. The cubic root of 205561 is about 59.0174227967.

It can be divided in two parts, 2055 and 61, that added together give a square (2116 = 46²).

The spelling of 205561 in words is "two hundred five thousand, five hundred sixty-one".