21121121112221 has 32 divisors (see below), whose sum is σ = 23547459167232. Its totient is φ = 18812961607680.

The previous prime is 21121121112197. The next prime is 21121121112233. The reversal of 21121121112221 is 12221112112112.

It is a happy number.

It is not a de Polignac number, because 21121121112221 - 2¹⁸ = 21121120850077 is a prime.

It is a super-2 number, since 2×21121121112221² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21121121112193 and 21121121112202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121121111221) 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, 894837206 + ... + 894860808.

It is an arithmetic number, because the mean of its divisors is an integer number (735858098976).

Almost surely, 2^{21121121112221} is an apocalyptic number.

It is an amenable number.

21121121112221 is a deficient number, since it is larger than the sum of its proper divisors (2426338055011).

21121121112221 is a wasteful number, since it uses less digits than its factorization.

21121121112221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29973.

The product of its digits is 64, while the sum is 20.

Adding to 21121121112221 its reverse (12221112112112), we get a palindrome (33342233224333).

The spelling of 21121121112221 in words is "twenty-one trillion, one hundred twenty-one billion, one hundred twenty-one million, one hundred twelve thousand, two hundred twenty-one".