9909 has 8 divisors (see below), whose sum is σ = 14720. Its totient is φ = 6588.

The previous prime is 9907. The next prime is 9923. The reversal of 9909 is 9099.

It is not a de Polignac number, because 9909 - 2¹ = 9907 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 367 = 9909 / (9 + 9 + 0 + 9).

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 157 + ... + 210.

It is an arithmetic number, because the mean of its divisors is an integer number (1840).

2⁹⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

9909 is a deficient number, since it is larger than the sum of its proper divisors (4811).

9909 is a wasteful number, since it uses less digits than its factorization.

9909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 376 (or 370 counting only the distinct ones).

The product of its (nonzero) digits is 729, while the sum is 27.

The square root of 9909 is about 99.5439601382. The cubic root of 9909 is about 21.4787964745.

Subtracting from 9909 its product of nonzero digits (729), we obtain a triangular number (9180 = T₁₃₅).

It can be divided in two parts, 990 and 9, that added together give a palindrome (999).

The spelling of 9909 in words is "nine thousand, nine hundred nine".