21121212111 has 16 divisors (see below), whose sum is σ = 29147520000. Its totient is φ = 13588350048.

The previous prime is 21121212103. The next prime is 21121212121. The reversal of 21121212111 is 11121212112.

It is a happy number.

It is not a de Polignac number, because 21121212111 - 2³ = 21121212103 is a prime.

It is a super-2 number, since 2×21121212111² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121212121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 113190 + ... + 234636.

It is an arithmetic number, because the mean of its divisors is an integer number (1821720000).

Almost surely, 2^21121212111 is an apocalyptic number.

21121212111 is a deficient number, since it is larger than the sum of its proper divisors (8026307889).

21121212111 is a wasteful number, since it uses less digits than its factorization.

21121212111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123478.

The product of its digits is 16, while the sum is 15.

Adding to 21121212111 its reverse (11121212112), we get a palindrome (32242424223).

Subtracting from 21121212111 its reverse (11121212112), we obtain a palindrome (9999999999).

The spelling of 21121212111 in words is "twenty-one billion, one hundred twenty-one million, two hundred twelve thousand, one hundred eleven".