21131212 has 12 divisors (see below), whose sum is σ = 38172736. Its totient is φ = 10224720.

The previous prime is 21131191. The next prime is 21131251. The reversal of 21131212 is 21213112.

It is a junction number, because it is equal to n+sod(n) for n = 21131192 and 21131201.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 85083 + ... + 85330.

Almost surely, 2^21131212 is an apocalyptic number.

It is an amenable number.

21131212 is a deficient number, since it is larger than the sum of its proper divisors (17041524).

21131212 is a wasteful number, since it uses less digits than its factorization.

21131212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 170448 (or 170446 counting only the distinct ones).

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

The square root of 21131212 is about 4596.8698045518. The cubic root of 21131212 is about 276.4658344774.

Adding to 21131212 its reverse (21213112), we get a palindrome (42344324).

The spelling of 21131212 in words is "twenty-one million, one hundred thirty-one thousand, two hundred twelve".