204991 has 4 divisors (see below), whose sum is σ = 215800. Its totient is φ = 194184.

The previous prime is 204983. The next prime is 205019. The reversal of 204991 is 199402.

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 204991 - 2³ = 204983 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 (204931) 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, 5376 + ... + 5413.

It is an arithmetic number, because the mean of its divisors is an integer number (53950).

2²⁰⁴⁹⁹¹ is an apocalyptic number.

204991 is a deficient number, since it is larger than the sum of its proper divisors (10809).

204991 is a wasteful number, since it uses less digits than its factorization.

204991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10808.

The product of its (nonzero) digits is 648, while the sum is 25.

The square root of 204991 is about 452.7593179604. The cubic root of 204991 is about 58.9628225039.

The spelling of 204991 in words is "two hundred four thousand, nine hundred ninety-one".