21311331 has 16 divisors (see below), whose sum is σ = 30422400. Its totient is φ = 13229568.

The previous prime is 21311261. The next prime is 21311347. The reversal of 21311331 is 13311312.

It is not a de Polignac number, because 21311331 - 2⁹ = 21310819 is a prime.

It is a super-2 number, since 2×21311331² = 908345657983122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21311331.

It is not an unprimeable number, because it can be changed into a prime (21301331) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 195 + ... + 6531.

It is an arithmetic number, because the mean of its divisors is an integer number (1901400).

Almost surely, 2^21311331 is an apocalyptic number.

21311331 is a deficient number, since it is larger than the sum of its proper divisors (9111069).

21311331 is a wasteful number, since it uses less digits than its factorization.

21311331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6418.

The product of its digits is 54, while the sum is 15.

The square root of 21311331 is about 4616.4197166202. The cubic root of 21311331 is about 277.2491296556.

Adding to 21311331 its reverse (13311312), we get a palindrome (34622643).

The spelling of 21311331 in words is "twenty-one million, three hundred eleven thousand, three hundred thirty-one".