20831 has 4 divisors (see below), whose sum is σ = 21432. Its totient is φ = 20232.

The previous prime is 20809. The next prime is 20849. The reversal of 20831 is 13802.

20831 is nontrivially palindromic in base 5.

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 20831 - 2¹⁴ = 4447 is a prime.

It is a super-2 number, since 2×20831² = 867861122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20231) 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, 245 + ... + 318.

It is an arithmetic number, because the mean of its divisors is an integer number (5358).

2²⁰⁸³¹ is an apocalyptic number.

20831 is a deficient number, since it is larger than the sum of its proper divisors (601).

20831 is an equidigital number, since it uses as much as digits as its factorization.

20831 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 600.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 20831 is about 144.3294841673. The cubic root of 20831 is about 27.5150331028.

The spelling of 20831 in words is "twenty thousand, eight hundred thirty-one".