21131212111 has 4 divisors (see below), whose sum is σ = 21385805112. Its totient is φ = 20876619112.

The previous prime is 21131212103. The next prime is 21131212127. The reversal of 21131212111 is 11121213112.

It is a happy number.

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 21131212111 - 2³ = 21131212103 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21131212511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 127296376 + ... + 127296541.

It is an arithmetic number, because the mean of its divisors is an integer number (5346451278).

Almost surely, 2^21131212111 is an apocalyptic number.

21131212111 is a deficient number, since it is larger than the sum of its proper divisors (254593001).

21131212111 is an equidigital number, since it uses as much as digits as its factorization.

21131212111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254593000.

The product of its digits is 24, while the sum is 16.

Adding to 21131212111 its reverse (11121213112), we get a palindrome (32252425223).

The spelling of 21131212111 in words is "twenty-one billion, one hundred thirty-one million, two hundred twelve thousand, one hundred eleven".