21212213 has 4 divisors (see below), whose sum is σ = 23140608. Its totient is φ = 19283820.

The previous prime is 21212197. The next prime is 21212239. The reversal of 21212213 is 31221212.

It is a happy number.

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 21212213 - 2⁴ = 21212197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212263) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 964181 + ... + 964202.

It is an arithmetic number, because the mean of its divisors is an integer number (5785152).

Almost surely, 2^21212213 is an apocalyptic number.

It is an amenable number.

21212213 is a deficient number, since it is larger than the sum of its proper divisors (1928395).

21212213 is a wasteful number, since it uses less digits than its factorization.

21212213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1928394.

The product of its digits is 48, while the sum is 14.

The square root of 21212213 is about 4605.6718293860. The cubic root of 21212213 is about 276.8186373356.

Adding to 21212213 its reverse (31221212), we get a palindrome (52433425).

It can be divided in two parts, 2121 and 2213, that added together give a palindrome (4334).

The spelling of 21212213 in words is "twenty-one million, two hundred twelve thousand, two hundred thirteen".