21813843 has 16 divisors (see below), whose sum is σ = 30905600. Its totient is φ = 13646880.

The previous prime is 21813833. The next prime is 21813877. The reversal of 21813843 is 34831812.

It is not a de Polignac number, because 21813843 - 2⁹ = 21813331 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is a self number, because there is not a number n which added to its sum of digits gives 21813843.

It is not an unprimeable number, because it can be changed into a prime (21813833) 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 15 ways as a sum of consecutive naturals, for example, 4458 + ... + 7968.

It is an arithmetic number, because the mean of its divisors is an integer number (1931600).

Almost surely, 2^21813843 is an apocalyptic number.

21813843 is a deficient number, since it is larger than the sum of its proper divisors (9091757).

21813843 is a wasteful number, since it uses less digits than its factorization.

21813843 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3642.

The product of its digits is 4608, while the sum is 30.

The square root of 21813843 is about 4670.5291991379. The cubic root of 21813843 is about 279.4113611718.

The spelling of 21813843 in words is "twenty-one million, eight hundred thirteen thousand, eight hundred forty-three".