21111213 has 4 divisors (see below), whose sum is σ = 28148288. Its totient is φ = 14074140.

The previous prime is 21111199. The next prime is 21111239. The reversal of 21111213 is 31211112.

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 not a de Polignac number, because 21111213 - 2⁴ = 21111197 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 (21111253) 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, 3518533 + ... + 3518538.

It is an arithmetic number, because the mean of its divisors is an integer number (7037072).

Almost surely, 2^21111213 is an apocalyptic number.

It is an amenable number.

21111213 is a deficient number, since it is larger than the sum of its proper divisors (7037075).

21111213 is an equidigital number, since it uses as much as digits as its factorization.

21111213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7037074.

The product of its digits is 12, while the sum is 12.

The square root of 21111213 is about 4594.6940050454. The cubic root of 21111213 is about 276.3785893570.

Adding to 21111213 its reverse (31211112), we get a palindrome (52322325).

The spelling of 21111213 in words is "twenty-one million, one hundred eleven thousand, two hundred thirteen".