21212312121 has 144 divisors (see below), whose sum is σ = 43010106048. Its totient is φ = 9895737600.

The previous prime is 21212312119. The next prime is 21212312137. The reversal of 21212312121 is 12121321212.

21212312121 is a `hidden beast` number, since 21 + 212 + 312 + 121 = 666.

It is not a de Polignac number, because 21212312121 - 2¹ = 21212312119 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21212312094 and 21212312103.

It is not an unprimeable number, because it can be changed into a prime (21212312171) by changing a digit.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 2328786 + ... + 2337876.

It is an arithmetic number, because the mean of its divisors is an integer number (298681292).

Almost surely, 2^21212312121 is an apocalyptic number.

21212312121 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21212312121 is an abundant number, since it is smaller than the sum of its proper divisors (21797793927).

21212312121 is a wasteful number, since it uses less digits than its factorization.

21212312121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9172 (or 9162 counting only the distinct ones).

The product of its digits is 96, while the sum is 18.

Adding to 21212312121 its reverse (12121321212), we get a palindrome (33333633333).

Subtracting from 21212312121 its reverse (12121321212), we obtain a palindrome (9090990909).

It can be divided in two parts, 21212 and 312121, that added together give a palindrome (333333).

The spelling of 21212312121 in words is "twenty-one billion, two hundred twelve million, three hundred twelve thousand, one hundred twenty-one".