21121221201221 has 8 divisors (see below), whose sum is σ = 21528843360024. Its totient is φ = 20716796079360.

The previous prime is 21121221201191. The next prime is 21121221201257. The reversal of 21121221201221 is 12210212212112.

It can be written as a sum of positive squares in 4 ways, for example, as 406106680225 + 20715114520996 = 637265^2 + 4551386^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21121221201221 is a prime.

It is a super-2 number, since 2×21121221201221² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21121221201193 and 21121221201202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121221231221) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 799245896 + ... + 799272321.

It is an arithmetic number, because the mean of its divisors is an integer number (2691105420003).

Almost surely, 2^{21121221201221} is an apocalyptic number.

It is an amenable number.

21121221201221 is a deficient number, since it is larger than the sum of its proper divisors (407622158803).

21121221201221 is a wasteful number, since it uses less digits than its factorization.

21121221201221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1598518471.

The product of its (nonzero) digits is 128, while the sum is 20.

Adding to 21121221201221 its reverse (12210212212112), we get a palindrome (33331433413333).

The spelling of 21121221201221 in words is "twenty-one trillion, one hundred twenty-one billion, two hundred twenty-one million, two hundred one thousand, two hundred twenty-one".