204865 has 4 divisors (see below), whose sum is σ = 245844. Its totient is φ = 163888.

The previous prime is 204859. The next prime is 204871. The reversal of 204865 is 568402.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 568402 = 2 ⋅284201.

It is an interprime number because it is at equal distance from previous prime (204859) and next prime (204871).

It can be written as a sum of positive squares in 2 ways, for example, as 152881 + 51984 = 391^2 + 228^2 .

It is a cyclic number.

It is not a de Polignac number, because 204865 - 2³ = 204857 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20482 + ... + 20491.

It is an arithmetic number, because the mean of its divisors is an integer number (61461).

2²⁰⁴⁸⁶⁵ is an apocalyptic number.

It is an amenable number.

204865 is a deficient number, since it is larger than the sum of its proper divisors (40979).

204865 is an equidigital number, since it uses as much as digits as its factorization.

204865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40978.

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 204865 is about 452.6201497945. The cubic root of 204865 is about 58.9507393094.

The spelling of 204865 in words is "two hundred four thousand, eight hundred sixty-five".