20819 has 4 divisors (see below), whose sum is σ = 21120. Its totient is φ = 20520.

The previous prime is 20809. The next prime is 20849. The reversal of 20819 is 91802.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 20819 - 2⁸ = 20563 is a prime.

It is a super-2 number, since 2×20819² = 866861522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20819.

It is not an unprimeable number, because it can be changed into a prime (20809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14 + ... + 204.

It is an arithmetic number, because the mean of its divisors is an integer number (5280).

2²⁰⁸¹⁹ is an apocalyptic number.

20819 is a deficient number, since it is larger than the sum of its proper divisors (301).

20819 is a wasteful number, since it uses less digits than its factorization.

20819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 300.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 20819 is about 144.2879066312. The cubic root of 20819 is about 27.5097486099.

The spelling of 20819 in words is "twenty thousand, eight hundred nineteen".