21212223221 has 4 divisors (see below), whose sum is σ = 24242540832. Its totient is φ = 18181905612.

The previous prime is 21212223199. The next prime is 21212223233. The reversal of 21212223221 is 12232221212.

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 21212223221 - 2¹⁰ = 21212222197 is a prime.

It is a super-2 number, since 2×21212223221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21212223193 and 21212223202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212223121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1515158795 + ... + 1515158808.

It is an arithmetic number, because the mean of its divisors is an integer number (6060635208).

Almost surely, 2^21212223221 is an apocalyptic number.

It is an amenable number.

21212223221 is a deficient number, since it is larger than the sum of its proper divisors (3030317611).

21212223221 is an equidigital number, since it uses as much as digits as its factorization.

21212223221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3030317610.

The product of its digits is 384, while the sum is 20.

Adding to 21212223221 its reverse (12232221212), we get a palindrome (33444444433).

The spelling of 21212223221 in words is "twenty-one billion, two hundred twelve million, two hundred twenty-three thousand, two hundred twenty-one".