20289 has 4 divisors (see below), whose sum is σ = 27056. Its totient is φ = 13524.

The previous prime is 20287. The next prime is 20297. The reversal of 20289 is 98202.

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 not a de Polignac number, because 20289 - 2¹ = 20287 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20287) 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, 3379 + ... + 3384.

It is an arithmetic number, because the mean of its divisors is an integer number (6764).

2²⁰²⁸⁹ is an apocalyptic number.

It is an amenable number.

20289 is a deficient number, since it is larger than the sum of its proper divisors (6767).

20289 is an equidigital number, since it uses as much as digits as its factorization.

20289 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6766.

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 20289 is about 142.4394608246. The cubic root of 20289 is about 27.2742958694.

The spelling of 20289 in words is "twenty thousand, two hundred eighty-nine".