21228811 has 2 divisors, whose sum is σ = 21228812. Its totient is φ = 21228810.

The previous prime is 21228797. The next prime is 21228829. The reversal of 21228811 is 11882212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21228811 - 2²³ = 12840203 is a prime.

It is equal to p_1343473 and since 21228811 and 1343473 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21228881) 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 as a sum of consecutive naturals, namely, 10614405 + 10614406.

It is an arithmetic number, because the mean of its divisors is an integer number (10614406).

Almost surely, 2^21228811 is an apocalyptic number.

21228811 is a deficient number, since it is larger than the sum of its proper divisors (1).

21228811 is an equidigital number, since it uses as much as digits as its factorization.

21228811 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21228811 is about 4607.4733857072. The cubic root of 21228811 is about 276.8908196183.

The spelling of 21228811 in words is "twenty-one million, two hundred twenty-eight thousand, eight hundred eleven".