21210212111221 has 16 divisors (see below), whose sum is σ = 24294386672640. Its totient is φ = 18139584677760.

The previous prime is 21210212111113. The next prime is 21210212111227. The reversal of 21210212111221 is 12211121201212.

It is a happy number.

It is not a de Polignac number, because 21210212111221 - 2¹⁵ = 21210212078453 is a prime.

It is a super-2 number, since 2×21210212111221² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210212111227) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22735441 + ... + 23649961.

It is an arithmetic number, because the mean of its divisors is an integer number (1518399167040).

Almost surely, 2^{21210212111221} is an apocalyptic number.

It is an amenable number.

21210212111221 is a deficient number, since it is larger than the sum of its proper divisors (3084174561419).

21210212111221 is an equidigital number, since it uses as much as digits as its factorization.

21210212111221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 921924.

The product of its (nonzero) digits is 64, while the sum is 19.

Adding to 21210212111221 its reverse (12211121201212), we get a palindrome (33421333312433).

The spelling of 21210212111221 in words is "twenty-one trillion, two hundred ten billion, two hundred twelve million, one hundred eleven thousand, two hundred twenty-one".