21111211221 has 8 divisors (see below), whose sum is σ = 28189862304. Its totient is φ = 14053350480.

The previous prime is 21111211217. The next prime is 21111211237. The reversal of 21111211221 is 12211211112.

It is a happy number.

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

It is not a de Polignac number, because 21111211221 - 2² = 21111211217 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21111211221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111211621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5195215 + ... + 5199276.

It is an arithmetic number, because the mean of its divisors is an integer number (3523732788).

Almost surely, 2^21111211221 is an apocalyptic number.

It is an amenable number.

21111211221 is a deficient number, since it is larger than the sum of its proper divisors (7078651083).

21111211221 is a wasteful number, since it uses less digits than its factorization.

21111211221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10395171.

The product of its digits is 16, while the sum is 15.

Adding to 21111211221 its reverse (12211211112), we get a palindrome (33322422333).

The spelling of 21111211221 in words is "twenty-one billion, one hundred eleven million, two hundred eleven thousand, two hundred twenty-one".