21011112121221 has 40 divisors (see below), whose sum is σ = 32129185841984. Its totient is φ = 13676420479680.

The previous prime is 21011112121211. The next prime is 21011112121261. The reversal of 21011112121221 is 12212121111012.

It is a happy number.

21011112121221 is a `hidden beast` number, since 210 + 1 + 1 + 112 + 121 + 221 = 666.

It is not a de Polignac number, because 21011112121221 - 2⁵ = 21011112121189 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21011112121194 and 21011112121203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011112121211) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 7962456 + ... + 10267566.

Almost surely, 2^{21011112121221} is an apocalyptic number.

It is an amenable number.

21011112121221 is a deficient number, since it is larger than the sum of its proper divisors (11118073720763).

21011112121221 is a wasteful number, since it uses less digits than its factorization.

21011112121221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2307783 (or 2307774 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 18.

Adding to 21011112121221 its reverse (12212121111012), we get a palindrome (33223233232233).

The spelling of 21011112121221 in words is "twenty-one trillion, eleven billion, one hundred twelve million, one hundred twenty-one thousand, two hundred twenty-one".