20009 has 8 divisors (see below), whose sum is σ = 23328. Its totient is φ = 16960.

The previous prime is 19997. The next prime is 20011. The reversal of 20009 is 90002.

20009 = T₁₇ + T₁₈ + ... + T₄₉.

20009 is an esthetic number in base 6, because in such base its adjacent digits differ by 1.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20009 - 2⁴ = 19993 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (11).

It is a Duffinian number.

20009 is a modest number, since divided by 9 gives 2 as remainder.

It is a plaindrome in base 7 and base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20029) 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 7 ways as a sum of consecutive naturals, for example, 134 + ... + 240.

It is an arithmetic number, because the mean of its divisors is an integer number (2916).

2²⁰⁰⁰⁹ is an apocalyptic number.

It is an amenable number.

20009 is a deficient number, since it is larger than the sum of its proper divisors (3319).

20009 is a wasteful number, since it uses less digits than its factorization.

20009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135.

The product of its (nonzero) digits is 18, while the sum is 11.

The square root of 20009 is about 141.4531724635. The cubic root of 20009 is about 27.1482471818.

Subtracting from 20009 its product of nonzero digits (18), we obtain a palindrome (19991).

Adding to 20009 its reverse (90002), we get a palindrome (110011).

The spelling of 20009 in words is "twenty thousand, nine".