205999 has 4 divisors (see below), whose sum is σ = 207936. Its totient is φ = 204064.

The previous prime is 205993. The next prime is 206009. The reversal of 205999 is 999502.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 205999 - 2³ = 205991 is a prime.

It is a Duffinian number.

205999 is a modest number, since divided by 999 gives 205 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205991) 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, 799 + ... + 1024.

It is an arithmetic number, because the mean of its divisors is an integer number (51984).

2²⁰⁵⁹⁹⁹ is an apocalyptic number.

205999 is a deficient number, since it is larger than the sum of its proper divisors (1937).

205999 is a wasteful number, since it uses less digits than its factorization.

205999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1936.

The product of its (nonzero) digits is 7290, while the sum is 34.

The square root of 205999 is about 453.8711270834. The cubic root of 205999 is about 59.0593102707.

It can be divided in two parts, 2059 and 99, that multiplied together give a triangular number (203841 = T₆₃₈).

The spelling of 205999 in words is "two hundred five thousand, nine hundred ninety-nine".