21131311 has 4 divisors (see below), whose sum is σ = 21213792. Its totient is φ = 21048832.

The previous prime is 21131293. The next prime is 21131317. The reversal of 21131311 is 11313112.

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 21131311 - 2⁷ = 21131183 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21131291 and 21131300.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21131317) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40855 + ... + 41368.

It is an arithmetic number, because the mean of its divisors is an integer number (5303448).

Almost surely, 2^21131311 is an apocalyptic number.

21131311 is a deficient number, since it is larger than the sum of its proper divisors (82481).

21131311 is an equidigital number, since it uses as much as digits as its factorization.

21131311 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82480.

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

The square root of 21131311 is about 4596.8805727363. The cubic root of 21131311 is about 276.4662662254.

Adding to 21131311 its reverse (11313112), we get a palindrome (32444423).

It can be divided in two parts, 2 and 1131311, that multiplied together give a palindrome (2262622).

The spelling of 21131311 in words is "twenty-one million, one hundred thirty-one thousand, three hundred eleven".