20869 has 4 divisors (see below), whose sum is σ = 21420. Its totient is φ = 20320.

The previous prime is 20857. The next prime is 20873. The reversal of 20869 is 96802.

20869 is nontrivially palindromic in base 8.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8100 + 12769 = 90^2 + 113^2 .

It is a cyclic number.

It is not a de Polignac number, because 20869 - 2⁹ = 20357 is a prime.

It is a super-2 number, since 2×20869² = 871030322, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20809) 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, 214 + ... + 295.

It is an arithmetic number, because the mean of its divisors is an integer number (5355).

2²⁰⁸⁶⁹ is an apocalyptic number.

It is an amenable number.

20869 is a deficient number, since it is larger than the sum of its proper divisors (551).

20869 is an equidigital number, since it uses as much as digits as its factorization.

20869 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 550.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 20869 is about 144.4610674196. The cubic root of 20869 is about 27.5317539535.

The spelling of 20869 in words is "twenty thousand, eight hundred sixty-nine".