205906 has 4 divisors (see below), whose sum is σ = 308862. Its totient is φ = 102952.

The previous prime is 205883. The next prime is 205913. The reversal of 205906 is 609502.

205906 = T₃₆₉ + T₃₇₀ + T₃₇₁.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 609502 = 2 ⋅304751.

It can be written as a sum of positive squares in only one way, i.e., 180625 + 25281 = 425^2 + 159^2 .

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 51475 + ... + 51478.

2²⁰⁵⁹⁰⁶ is an apocalyptic number.

205906 is the 371-st centered triangular number.

205906 is a deficient number, since it is larger than the sum of its proper divisors (102956).

205906 is a wasteful number, since it uses less digits than its factorization.

205906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102955.

The product of its (nonzero) digits is 540, while the sum is 22.

The square root of 205906 is about 453.7686635280. The cubic root of 205906 is about 59.0504213237.

It can be divided in two parts, 205 and 906, that added together give a palindrome (1111).

The spelling of 205906 in words is "two hundred five thousand, nine hundred six".