21211221021 has 4 divisors (see below), whose sum is σ = 28281628032. Its totient is φ = 14140814012.

The previous prime is 21211221019. The next prime is 21211221061. The reversal of 21211221021 is 12012211212.

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 21211221021 - 2¹ = 21211221019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211221061) 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, 3535203501 + ... + 3535203506.

It is an arithmetic number, because the mean of its divisors is an integer number (7070407008).

Almost surely, 2^21211221021 is an apocalyptic number.

It is an amenable number.

21211221021 is a deficient number, since it is larger than the sum of its proper divisors (7070407011).

21211221021 is an equidigital number, since it uses as much as digits as its factorization.

21211221021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7070407010.

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

Adding to 21211221021 its reverse (12012211212), we get a palindrome (33223432233).

The spelling of 21211221021 in words is "twenty-one billion, two hundred eleven million, two hundred twenty-one thousand, twenty-one".