85821 has 4 divisors (see below), whose sum is σ = 114432. Its totient is φ = 57212.

The previous prime is 85819. The next prime is 85829. The reversal of 85821 is 12858.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 85821 - 2¹ = 85819 is a prime.

It is a D-number.

85821 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 85791 and 85800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (85829) 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 3 ways as a sum of consecutive naturals, for example, 14301 + ... + 14306.

It is an arithmetic number, because the mean of its divisors is an integer number (28608).

2⁸⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

85821 is a deficient number, since it is larger than the sum of its proper divisors (28611).

85821 is a wasteful number, since it uses less digits than its factorization.

85821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28610.

The product of its digits is 640, while the sum is 24.

The square root of 85821 is about 292.9522145334. The cubic root of 85821 is about 44.1094040547.

The spelling of 85821 in words is "eighty-five thousand, eight hundred twenty-one".