205109 has 4 divisors (see below), whose sum is σ = 206016. Its totient is φ = 204204.

The previous prime is 205103. The next prime is 205111. The reversal of 205109 is 901502.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205109 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 (205103) 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, 212 + ... + 674.

It is an arithmetic number, because the mean of its divisors is an integer number (51504).

2²⁰⁵¹⁰⁹ is an apocalyptic number.

It is an amenable number.

205109 is a deficient number, since it is larger than the sum of its proper divisors (907).

205109 is an equidigital number, since it uses as much as digits as its factorization.

205109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 906.

The product of its (nonzero) digits is 90, while the sum is 17.

The square root of 205109 is about 452.8896112741. The cubic root of 205109 is about 58.9741340224.

The spelling of 205109 in words is "two hundred five thousand, one hundred nine".