21211213 has 4 divisors (see below), whose sum is σ = 21292128. Its totient is φ = 21130300.

The previous prime is 21211181. The next prime is 21211217. The reversal of 21211213 is 31211212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21211213 - 2⁵ = 21211181 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21211193 and 21211202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211217) 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, 40063 + ... + 40588.

It is an arithmetic number, because the mean of its divisors is an integer number (5323032).

Almost surely, 2^21211213 is an apocalyptic number.

It is an amenable number.

21211213 is a deficient number, since it is larger than the sum of its proper divisors (80915).

21211213 is an equidigital number, since it uses as much as digits as its factorization.

21211213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80914.

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

The square root of 21211213 is about 4605.5632663117. The cubic root of 21211213 is about 276.8142872789.

Adding to 21211213 its reverse (31211212), we get a palindrome (52422425).

Subtracting 21211213 from its reverse (31211212), we obtain a palindrome (9999999).

The spelling of 21211213 in words is "twenty-one million, two hundred eleven thousand, two hundred thirteen".