20209 has 4 divisors (see below), whose sum is σ = 23104. Its totient is φ = 17316.

The previous prime is 20201. The next prime is 20219. The reversal of 20209 is 90202.

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 a cyclic number.

It is not a de Polignac number, because 20209 - 2³ = 20201 is a prime.

It is a magnanimous number.

It is a Duffinian number.

It is a nialpdrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20201) 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, 1437 + ... + 1450.

It is an arithmetic number, because the mean of its divisors is an integer number (5776).

2²⁰²⁰⁹ is an apocalyptic number.

It is an amenable number.

20209 is a deficient number, since it is larger than the sum of its proper divisors (2895).

20209 is an equidigital number, since it uses as much as digits as its factorization.

20209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2894.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 20209 is about 142.1583623991. The cubic root of 20209 is about 27.2384009216.

The spelling of 20209 in words is "twenty thousand, two hundred nine".