21123211 has 2 divisors, whose sum is σ = 21123212. Its totient is φ = 21123210.

The previous prime is 21123187. The next prime is 21123287. The reversal of 21123211 is 11232112.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123211 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21123191 and 21123200.

It is not a weakly prime, because it can be changed into another prime (21123511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561605 + 10561606.

It is an arithmetic number, because the mean of its divisors is an integer number (10561606).

Almost surely, 2^21123211 is an apocalyptic number.

21123211 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123211 is an equidigital number, since it uses as much as digits as its factorization.

21123211 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24, while the sum is 13.

The square root of 21123211 is about 4595.9994560487. Note that the first 3 decimals coincide. The cubic root of 21123211 is about 276.4309369306.

Adding to 21123211 its reverse (11232112), we get a palindrome (32355323).

It can be divided in two parts, 2 and 1123211, that multiplied together give a palindrome (2246422).

The spelling of 21123211 in words is "twenty-one million, one hundred twenty-three thousand, two hundred eleven".