21002122120021 has 4 divisors (see below), whose sum is σ = 24002425280032. Its totient is φ = 18001818960012.

The previous prime is 21002122120019. The next prime is 21002122120033. The reversal of 21002122120021 is 12002122120012.

It is a happy number.

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 21002122120021 - 2¹ = 21002122120019 is a prime.

It is a super-3 number, since 3×21002122120021³ (a number of 41 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21002122119977 and 21002122120004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002122120121) 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, 1500151579995 + ... + 1500151580008.

It is an arithmetic number, because the mean of its divisors is an integer number (6000606320008).

Almost surely, 2^{21002122120021} is an apocalyptic number.

It is an amenable number.

21002122120021 is a deficient number, since it is larger than the sum of its proper divisors (3000303160011).

21002122120021 is an equidigital number, since it uses as much as digits as its factorization.

21002122120021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3000303160010.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21002122120021 its reverse (12002122120012), we get a palindrome (33004244240033).

Subtracting from 21002122120021 its reverse (12002122120012), we obtain a palindrome (9000000000009).

The spelling of 21002122120021 in words is "twenty-one trillion, two billion, one hundred twenty-two million, one hundred twenty thousand, twenty-one".