285821 has 12 divisors (see below), whose sum is σ = 324192. Its totient is φ = 251328.

The previous prime is 285781. The next prime is 285823. The reversal of 285821 is 128582.

It is not a de Polignac number, because 285821 - 2⁶ = 285757 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 (285823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6626 + ... + 6668.

It is an arithmetic number, because the mean of its divisors is an integer number (27016).

2²⁸⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

285821 is a deficient number, since it is larger than the sum of its proper divisors (38371).

285821 is a wasteful number, since it uses less digits than its factorization.

285821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100 (or 83 counting only the distinct ones).

The product of its digits is 1280, while the sum is 26.

The square root of 285821 is about 534.6222965796. The cubic root of 285821 is about 65.8715745704.

The spelling of 285821 in words is "two hundred eighty-five thousand, eight hundred twenty-one".