21031211 has 4 divisors (see below), whose sum is σ = 21041424. Its totient is φ = 21021000.

The previous prime is 21031187. The next prime is 21031217. The reversal of 21031211 is 11213012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21031211 - 2¹⁰ = 21030187 is a prime.

It is a super-2 number, since 2×21031211² = 884623672253042, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21031192 and 21031201.

It is not an unprimeable number, because it can be changed into a prime (21031217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 815 + ... + 6536.

It is an arithmetic number, because the mean of its divisors is an integer number (5260356).

Almost surely, 2^21031211 is an apocalyptic number.

21031211 is a deficient number, since it is larger than the sum of its proper divisors (10213).

21031211 is an equidigital number, since it uses as much as digits as its factorization.

21031211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10212.

The product of its (nonzero) digits is 12, while the sum is 11.

The square root of 21031211 is about 4585.9798298728. The cubic root of 21031211 is about 276.0290305878.

Adding to 21031211 its reverse (11213012), we get a palindrome (32244223).

The spelling of 21031211 in words is "twenty-one million, thirty-one thousand, two hundred eleven".