21212202221 has 8 divisors (see below), whose sum is σ = 25078465920. Its totient is φ = 17554925808.

The previous prime is 21212202173. The next prime is 21212202227. The reversal of 21212202221 is 12220221212.

It is a happy number.

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

It is a de Polignac number, because none of the positive numbers 2^k-21212202221 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21212202221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212202227) 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, 52246601 + ... + 52247006.

It is an arithmetic number, because the mean of its divisors is an integer number (3134808240).

Almost surely, 2^21212202221 is an apocalyptic number.

It is an amenable number.

21212202221 is a deficient number, since it is larger than the sum of its proper divisors (3866263699).

21212202221 is a wasteful number, since it uses less digits than its factorization.

21212202221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104493643.

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21212202221 its reverse (12220221212), we get a palindrome (33432423433).

The spelling of 21212202221 in words is "twenty-one billion, two hundred twelve million, two hundred two thousand, two hundred twenty-one".