21211211221221 has 32 divisors (see below), whose sum is σ = 34489063920640. Its totient is φ = 11325462850944.

The previous prime is 21211211221217. The next prime is 21211211221253. The reversal of 21211211221221 is 12212211211212.

It is not a de Polignac number, because 21211211221221 - 2² = 21211211221217 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211211221201) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 364086835 + ... + 364145088.

It is an arithmetic number, because the mean of its divisors is an integer number (1077783247520).

Almost surely, 2^{21211211221221} is an apocalyptic number.

21211211221221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21211211221221 is a deficient number, since it is larger than the sum of its proper divisors (13277852699419).

21211211221221 is a wasteful number, since it uses less digits than its factorization.

21211211221221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 728232025.

The product of its digits is 128, while the sum is 21.

Adding to 21211211221221 its reverse (12212211211212), we get a palindrome (33423422432433).

The spelling of 21211211221221 in words is "twenty-one trillion, two hundred eleven billion, two hundred eleven million, two hundred twenty-one thousand, two hundred twenty-one".