20609 has 4 divisors (see below), whose sum is σ = 21204. Its totient is φ = 20016.

The previous prime is 20599. The next prime is 20611. The reversal of 20609 is 90602.

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 10000 + 10609 = 100^2 + 103^2 .

It is a cyclic number.

It is not a de Polignac number, because 20609 - 2⁴ = 20593 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20639) 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, 242 + ... + 315.

It is an arithmetic number, because the mean of its divisors is an integer number (5301).

2²⁰⁶⁰⁹ is an apocalyptic number.

It is an amenable number.

20609 is a deficient number, since it is larger than the sum of its proper divisors (595).

20609 is an equidigital number, since it uses as much as digits as its factorization.

20609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 594.

The product of its (nonzero) digits is 108, while the sum is 17.

The square root of 20609 is about 143.5583505060. The cubic root of 20609 is about 27.4169394606.

The spelling of 20609 in words is "twenty thousand, six hundred nine".