21212231221 has 8 divisors (see below), whose sum is σ = 22083460920. Its totient is φ = 20350319808.

The previous prime is 21212231207. The next prime is 21212231231. The reversal of 21212231221 is 12213221212.

It can be written as a sum of positive squares in 4 ways, for example, as 6055174225 + 15157056996 = 77815^2 + 123114^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21212231221 - 2¹⁹ = 21211706933 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212231231) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2324926 + ... + 2334031.

It is an arithmetic number, because the mean of its divisors is an integer number (2760432615).

Almost surely, 2^21212231221 is an apocalyptic number.

It is an amenable number.

21212231221 is a deficient number, since it is larger than the sum of its proper divisors (871229699).

21212231221 is a wasteful number, since it uses less digits than its factorization.

21212231221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4659143.

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

Adding to 21212231221 its reverse (12213221212), we get a palindrome (33425452433).

The spelling of 21212231221 in words is "twenty-one billion, two hundred twelve million, two hundred thirty-one thousand, two hundred twenty-one".