11991809 has 8 divisors (see below), whose sum is σ = 12726720. Its totient is φ = 11274736.

The previous prime is 11991781. The next prime is 11991839. The reversal of 11991809 is 90819911.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-11991809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (11991839) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3062 + ... + 5775.

It is an arithmetic number, because the mean of its divisors is an integer number (1590840).

Almost surely, 2^11991809 is an apocalyptic number.

It is an amenable number.

11991809 is a deficient number, since it is larger than the sum of its proper divisors (734911).

11991809 is an equidigital number, since it uses as much as digits as its factorization.

11991809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8919.

The product of its (nonzero) digits is 5832, while the sum is 38.

The square root of 11991809 is about 3462.9191443059. The cubic root of 11991809 is about 228.8907457965.

The spelling of 11991809 in words is "eleven million, nine hundred ninety-one thousand, eight hundred nine".