11820821 has 4 divisors (see below), whose sum is σ = 11828172. Its totient is φ = 11813472.

The previous prime is 11820803. The next prime is 11820839. The reversal of 11820821 is 12802811.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12802811 = 7 ⋅1828973.

It is an interprime number because it is at equal distance from previous prime (11820803) and next prime (11820839).

It can be written as a sum of positive squares in 2 ways, for example, as 6180196 + 5640625 = 2486^2 + 2375^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-11820821 is a prime.

It is a super-2 number, since 2×11820821² = 279463618228082, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11820841) 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 3 ways as a sum of consecutive naturals, for example, 110 + ... + 4863.

It is an arithmetic number, because the mean of its divisors is an integer number (2957043).

Almost surely, 2^11820821 is an apocalyptic number.

It is an amenable number.

11820821 is a deficient number, since it is larger than the sum of its proper divisors (7351).

11820821 is an equidigital number, since it uses as much as digits as its factorization.

11820821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7350.

The product of its (nonzero) digits is 256, while the sum is 23.

The square root of 11820821 is about 3438.1420854875. The cubic root of 11820821 is about 227.7976364381.

The spelling of 11820821 in words is "eleven million, eight hundred twenty thousand, eight hundred twenty-one".