21816211 has 4 divisors (see below), whose sum is σ = 21930624. Its totient is φ = 21701800.

The previous prime is 21816209. The next prime is 21816217. The reversal of 21816211 is 11261812.

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 21816211 - 2¹ = 21816209 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21816217) 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, 56920 + ... + 57301.

It is an arithmetic number, because the mean of its divisors is an integer number (5482656).

Almost surely, 2^21816211 is an apocalyptic number.

21816211 is a deficient number, since it is larger than the sum of its proper divisors (114413).

21816211 is a wasteful number, since it uses less digits than its factorization.

21816211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 114412.

The product of its digits is 192, while the sum is 22.

The square root of 21816211 is about 4670.7826967223. The cubic root of 21816211 is about 279.4214712987.

The spelling of 21816211 in words is "twenty-one million, eight hundred sixteen thousand, two hundred eleven".