21840811 has 4 divisors (see below), whose sum is σ = 22066072. Its totient is φ = 21615552.

The previous prime is 21840809. The next prime is 21840817. The reversal of 21840811 is 11804812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21840811 - 2¹ = 21840809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21840817) 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, 112485 + ... + 112678.

It is an arithmetic number, because the mean of its divisors is an integer number (5516518).

Almost surely, 2^21840811 is an apocalyptic number.

21840811 is a deficient number, since it is larger than the sum of its proper divisors (225261).

21840811 is an equidigital number, since it uses as much as digits as its factorization.

21840811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 225260.

The product of its (nonzero) digits is 512, while the sum is 25.

The square root of 21840811 is about 4673.4153464035. The cubic root of 21840811 is about 279.5264572376.

The spelling of 21840811 in words is "twenty-one million, eight hundred forty thousand, eight hundred eleven".