21121202121221 has 4 divisors (see below), whose sum is σ = 21121225261344. Its totient is φ = 21121178981100.

The previous prime is 21121202121073. The next prime is 21121202121241. The reversal of 21121202121221 is 12212120212112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21121202121221 - 2¹⁸ = 21121201859077 is a prime.

It is a super-2 number, since 2×21121202121221² (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 = 21121202121193 and 21121202121202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121202121241) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10142195 + ... + 12046016.

It is an arithmetic number, because the mean of its divisors is an integer number (5280306315336).

Almost surely, 2^{21121202121221} is an apocalyptic number.

It is an amenable number.

21121202121221 is a deficient number, since it is larger than the sum of its proper divisors (23140123).

21121202121221 is an equidigital number, since it uses as much as digits as its factorization.

21121202121221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23140122.

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

Adding to 21121202121221 its reverse (12212120212112), we get a palindrome (33333322333333).

The spelling of 21121202121221 in words is "twenty-one trillion, one hundred twenty-one billion, two hundred two million, one hundred twenty-one thousand, two hundred twenty-one".