11891809 has 4 divisors (see below), whose sum is σ = 11930116. Its totient is φ = 11853504.

The previous prime is 11891801. The next prime is 11891813. The reversal of 11891809 is 90819811.

It is a happy number.

11891809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 140625 + 11751184 = 375^2 + 3428^2 .

It is a cyclic number.

It is not a de Polignac number, because 11891809 - 2³ = 11891801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (11891801) 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, 18684 + ... + 19309.

It is an arithmetic number, because the mean of its divisors is an integer number (2982529).

Almost surely, 2^11891809 is an apocalyptic number.

It is an amenable number.

11891809 is a deficient number, since it is larger than the sum of its proper divisors (38307).

11891809 is an equidigital number, since it uses as much as digits as its factorization.

11891809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38306.

The product of its (nonzero) digits is 5184, while the sum is 37.

The square root of 11891809 is about 3448.4502316258. The cubic root of 11891809 is about 228.2527270962.

The spelling of 11891809 in words is "eleven million, eight hundred ninety-one thousand, eight hundred nine".