21212132221 has 4 divisors (see below), whose sum is σ = 24242436832. Its totient is φ = 18181827612.

The previous prime is 21212132197. The next prime is 21212132233. The reversal of 21212132221 is 12223121212.

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 21212132221 - 2⁷ = 21212132093 is a prime.

It is a super-2 number, since 2×21212132221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212132251) 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, 1515152295 + ... + 1515152308.

It is an arithmetic number, because the mean of its divisors is an integer number (6060609208).

Almost surely, 2^21212132221 is an apocalyptic number.

It is an amenable number.

21212132221 is a deficient number, since it is larger than the sum of its proper divisors (3030304611).

21212132221 is an equidigital number, since it uses as much as digits as its factorization.

21212132221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3030304610.

The product of its digits is 192, while the sum is 19.

Adding to 21212132221 its reverse (12223121212), we get a palindrome (33435253433).

The spelling of 21212132221 in words is "twenty-one billion, two hundred twelve million, one hundred thirty-two thousand, two hundred twenty-one".