21213311 has 4 divisors (see below), whose sum is σ = 24243792. Its totient is φ = 18182832.

The previous prime is 21213293. The next prime is 21213341. The reversal of 21213311 is 11331212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21213311 - 2²² = 17019007 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 (21213341) 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, 1515230 + ... + 1515243.

It is an arithmetic number, because the mean of its divisors is an integer number (6060948).

Almost surely, 2^21213311 is an apocalyptic number.

21213311 is a deficient number, since it is larger than the sum of its proper divisors (3030481).

21213311 is an equidigital number, since it uses as much as digits as its factorization.

21213311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3030480.

The product of its digits is 36, while the sum is 14.

The square root of 21213311 is about 4605.7910286942. The cubic root of 21213311 is about 276.8234135404.

Adding to 21213311 its reverse (11331212), we get a palindrome (32544523).

The spelling of 21213311 in words is "twenty-one million, two hundred thirteen thousand, three hundred eleven".