21165211 has 4 divisors (see below), whose sum is σ = 21213432. Its totient is φ = 21116992.

The previous prime is 21165197. The next prime is 21165227. The reversal of 21165211 is 11256112.

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 21165211 - 2²¹ = 19068059 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21165241) 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, 23446 + ... + 24331.

It is an arithmetic number, because the mean of its divisors is an integer number (5303358).

Almost surely, 2^21165211 is an apocalyptic number.

21165211 is a deficient number, since it is larger than the sum of its proper divisors (48221).

21165211 is an equidigital number, since it uses as much as digits as its factorization.

21165211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48220.

The product of its digits is 120, while the sum is 19.

The square root of 21165211 is about 4600.5663781756. The cubic root of 21165211 is about 276.6140279850.

Subtracting from 21165211 its reverse (11256112), we obtain a palindrome (9909099).

The spelling of 21165211 in words is "twenty-one million, one hundred sixty-five thousand, two hundred eleven".