20823 has 8 divisors (see below), whose sum is σ = 30336. Its totient is φ = 12600.

The previous prime is 20809. The next prime is 20849. The reversal of 20823 is 32802.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20823 - 2⁴ = 20807 is a prime.

It is a Smith number, since the sum of its digits (15) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

20823 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20873) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 283 + ... + 348.

It is an arithmetic number, because the mean of its divisors is an integer number (3792).

2²⁰⁸²³ is an apocalyptic number.

20823 is a deficient number, since it is larger than the sum of its proper divisors (9513).

20823 is a wasteful number, since it uses less digits than its factorization.

20823 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 645.

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 20823 is about 144.3017671409. The cubic root of 20823 is about 27.5115103331.

It can be divided in two parts, 208 and 23, that added together give a triangular number (231 = T₂₁).

The spelling of 20823 in words is "twenty thousand, eight hundred twenty-three".