21221311 has 4 divisors (see below), whose sum is σ = 21233800. Its totient is φ = 21208824.

The previous prime is 21221303. The next prime is 21221339. The reversal of 21221311 is 11312212.

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 21221311 - 2³ = 21221303 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21221291 and 21221300.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221371) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3201 + ... + 7258.

It is an arithmetic number, because the mean of its divisors is an integer number (5308450).

Almost surely, 2^21221311 is an apocalyptic number.

21221311 is a deficient number, since it is larger than the sum of its proper divisors (12489).

21221311 is a wasteful number, since it uses less digits than its factorization.

21221311 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12488.

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

The square root of 21221311 is about 4606.6594187111. The cubic root of 21221311 is about 276.8582078727.

Adding to 21221311 its reverse (11312212), we get a palindrome (32533523).

Subtracting from 21221311 its reverse (11312212), we obtain a palindrome (9909099).

The spelling of 21221311 in words is "twenty-one million, two hundred twenty-one thousand, three hundred eleven".