21212120121 has 4 divisors (see below), whose sum is σ = 28282826832. Its totient is φ = 14141413412.

The previous prime is 21212120099. The next prime is 21212120123. The reversal of 21212120121 is 12102121212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21212120121 - 2⁵ = 21212120089 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21212120121.

It is not an unprimeable number, because it can be changed into a prime (21212120123) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3535353351 + ... + 3535353356.

It is an arithmetic number, because the mean of its divisors is an integer number (7070706708).

Almost surely, 2^21212120121 is an apocalyptic number.

It is an amenable number.

21212120121 is a deficient number, since it is larger than the sum of its proper divisors (7070706711).

21212120121 is an equidigital number, since it uses as much as digits as its factorization.

21212120121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7070706710.

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 21212120121 its reverse (12102121212), we get a palindrome (33314241333).

The spelling of 21212120121 in words is "twenty-one billion, two hundred twelve million, one hundred twenty thousand, one hundred twenty-one".