11821813 has 4 divisors (see below), whose sum is σ = 11930380. Its totient is φ = 11713248.

The previous prime is 11821787. The next prime is 11821841. The reversal of 11821813 is 31812811.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31812811 = 2267 ⋅14033.

It can be written as a sum of positive squares in 2 ways, for example, as 9381969 + 2439844 = 3063^2 + 1562^2 .

It is a cyclic number.

It is not a de Polignac number, because 11821813 - 2⁹ = 11821301 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11821853) 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, 54120 + ... + 54337.

It is an arithmetic number, because the mean of its divisors is an integer number (2982595).

Almost surely, 2^11821813 is an apocalyptic number.

It is an amenable number.

11821813 is a deficient number, since it is larger than the sum of its proper divisors (108567).

11821813 is a wasteful number, since it uses less digits than its factorization.

11821813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108566.

The product of its digits is 384, while the sum is 25.

The square root of 11821813 is about 3438.2863464232. The cubic root of 11821813 is about 227.8040084979.

The spelling of 11821813 in words is "eleven million, eight hundred twenty-one thousand, eight hundred thirteen".