11805535821 has 4 divisors (see below), whose sum is σ = 15740714432. Its totient is φ = 7870357212.

The previous prime is 11805535817. The next prime is 11805535831. The reversal of 11805535821 is 12853550811.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12853550811 = 3 ⋅4284516937.

It is not a de Polignac number, because 11805535821 - 2² = 11805535817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 11805535821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11805535831) 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, 1967589301 + ... + 1967589306.

It is an arithmetic number, because the mean of its divisors is an integer number (3935178608).

Almost surely, 2^11805535821 is an apocalyptic number.

It is an amenable number.

11805535821 is a deficient number, since it is larger than the sum of its proper divisors (3935178611).

11805535821 is an equidigital number, since it uses as much as digits as its factorization.

11805535821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3935178610.

The product of its (nonzero) digits is 48000, while the sum is 39.

The spelling of 11805535821 in words is "eleven billion, eight hundred five million, five hundred thirty-five thousand, eight hundred twenty-one".