21311311 has 4 divisors (see below), whose sum is σ = 24355792. Its totient is φ = 18266832.

The previous prime is 21311261. The next prime is 21311347. The reversal of 21311311 is 11311312.

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 21311311 - 2¹¹ = 21309263 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21311291 and 21311300.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311111) 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, 1522230 + ... + 1522243.

It is an arithmetic number, because the mean of its divisors is an integer number (6088948).

Almost surely, 2^21311311 is an apocalyptic number.

21311311 is a deficient number, since it is larger than the sum of its proper divisors (3044481).

21311311 is an equidigital number, since it uses as much as digits as its factorization.

21311311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3044480.

The product of its digits is 18, while the sum is 13.

The square root of 21311311 is about 4616.4175504389. The cubic root of 21311311 is about 277.2490429258.

Adding to 21311311 its reverse (11311312), we get a palindrome (32622623).

Subtracting from 21311311 its reverse (11311312), we obtain a palindrome (9999999).

The spelling of 21311311 in words is "twenty-one million, three hundred eleven thousand, three hundred eleven".