285991 has 4 divisors (see below), whose sum is σ = 302832. Its totient is φ = 269152.

The previous prime is 285983. The next prime is 285997. The reversal of 285991 is 199582.

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 285991 - 2³ = 285983 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 (285997) 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, 8395 + ... + 8428.

It is an arithmetic number, because the mean of its divisors is an integer number (75708).

2²⁸⁵⁹⁹¹ is an apocalyptic number.

285991 is a deficient number, since it is larger than the sum of its proper divisors (16841).

285991 is a wasteful number, since it uses less digits than its factorization.

285991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16840.

The product of its digits is 6480, while the sum is 34.

The square root of 285991 is about 534.7812636957. The cubic root of 285991 is about 65.8846316332.

The spelling of 285991 in words is "two hundred eighty-five thousand, nine hundred ninety-one".