11813640821 has 4 divisors (see below), whose sum is σ = 12101778444. Its totient is φ = 11525503200.

The previous prime is 11813640791. The next prime is 11813640863. The reversal of 11813640821 is 12804631811.

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 5054499025 + 6759141796 = 71095^2 + 82214^2 .

It is a cyclic number.

It is not a de Polignac number, because 11813640821 - 2⁶ = 11813640757 is a prime.

It is a super-3 number, since 3×11813640821³ (a number of 31 digits) contains 333 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 (11813640521) 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, 144068750 + ... + 144068831.

It is an arithmetic number, because the mean of its divisors is an integer number (3025444611).

Almost surely, 2^11813640821 is an apocalyptic number.

It is an amenable number.

11813640821 is a deficient number, since it is larger than the sum of its proper divisors (288137623).

11813640821 is an equidigital number, since it uses as much as digits as its factorization.

11813640821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 288137622.

The product of its (nonzero) digits is 9216, while the sum is 35.

The spelling of 11813640821 in words is "eleven billion, eight hundred thirteen million, six hundred forty thousand, eight hundred twenty-one".