21121221211 has 4 divisors (see below), whose sum is σ = 21121908712. Its totient is φ = 21120533712.

The previous prime is 21121221193. The next prime is 21121221221. The reversal of 21121221211 is 11212212112.

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 21121221211 - 2⁷ = 21121221083 is a prime.

It is a super-2 number, since 2×21121221211² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21121221221) 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, 295401 + ... + 359866.

It is an arithmetic number, because the mean of its divisors is an integer number (5280477178).

Almost surely, 2^21121221211 is an apocalyptic number.

21121221211 is a deficient number, since it is larger than the sum of its proper divisors (687501).

21121221211 is an equidigital number, since it uses as much as digits as its factorization.

21121221211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 687500.

The product of its digits is 32, while the sum is 16.

Adding to 21121221211 its reverse (11212212112), we get a palindrome (32333433323).

Subtracting from 21121221211 its reverse (11212212112), we obtain a palindrome (9909009099).

It can be divided in two parts, 2 and 1121221211, that multiplied together give a palindrome (2242442422).

The spelling of 21121221211 in words is "twenty-one billion, one hundred twenty-one million, two hundred twenty-one thousand, two hundred eleven".