21212331 has 16 divisors (see below), whose sum is σ = 32527104. Its totient is φ = 12045024.

The previous prime is 21212297. The next prime is 21212353. The reversal of 21212331 is 13321212.

It is not a de Polignac number, because 21212331 - 2¹¹ = 21210283 is a prime.

It is a super-2 number, since 2×21212331² = 899925972907122, 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 21212331.

It is not an unprimeable number, because it can be changed into a prime (21212131) 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, 325 + ... + 6521.

It is an arithmetic number, because the mean of its divisors is an integer number (2032944).

Almost surely, 2^21212331 is an apocalyptic number.

21212331 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21212331 is a deficient number, since it is larger than the sum of its proper divisors (11314773).

21212331 is a wasteful number, since it uses less digits than its factorization.

21212331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6370.

The product of its digits is 72, while the sum is 15.

The square root of 21212331 is about 4605.6846396600. The cubic root of 21212331 is about 276.8191506333.

Adding to 21212331 its reverse (13321212), we get a palindrome (34533543).

The spelling of 21212331 in words is "twenty-one million, two hundred twelve thousand, three hundred thirty-one".