21021211221 has 8 divisors (see below), whose sum is σ = 28112960544. Its totient is φ = 13971801360.

The previous prime is 21021211219. The next prime is 21021211247. The reversal of 21021211221 is 12211212012.

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

It is not a de Polignac number, because 21021211221 - 2¹ = 21021211219 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21021211221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021211021) 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 7 ways as a sum of consecutive naturals, for example, 10583706 + ... + 10585691.

It is an arithmetic number, because the mean of its divisors is an integer number (3514120068).

Almost surely, 2^21021211221 is an apocalyptic number.

It is an amenable number.

21021211221 is a deficient number, since it is larger than the sum of its proper divisors (7091749323).

21021211221 is a wasteful number, since it uses less digits than its factorization.

21021211221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21169731.

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

Adding to 21021211221 its reverse (12211212012), we get a palindrome (33232423233).

The spelling of 21021211221 in words is "twenty-one billion, twenty-one million, two hundred eleven thousand, two hundred twenty-one".