21002121001021 has 4 divisors (see below), whose sum is σ = 22237539883452. Its totient is φ = 19766702118592.

The previous prime is 21002121001019. The next prime is 21002121001063. The reversal of 21002121001021 is 12010012120012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15471745695396 + 5530375305625 = 3933414^2 + 2351675^2 .

It is a cyclic number.

It is not a de Polignac number, because 21002121001021 - 2¹ = 21002121001019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21002121000992 and 21002121001010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002121001321) 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, 617709441190 + ... + 617709441223.

It is an arithmetic number, because the mean of its divisors is an integer number (5559384970863).

Almost surely, 2^{21002121001021} is an apocalyptic number.

It is an amenable number.

21002121001021 is a deficient number, since it is larger than the sum of its proper divisors (1235418882431).

21002121001021 is a wasteful number, since it uses less digits than its factorization.

21002121001021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1235418882430.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21002121001021 its reverse (12010012120012), we get a palindrome (33012133121033).

The spelling of 21002121001021 in words is "twenty-one trillion, two billion, one hundred twenty-one million, one thousand, twenty-one".