21001202020121 has 4 divisors (see below), whose sum is σ = 22236566844852. Its totient is φ = 19765837195392.

The previous prime is 21001202020093. The next prime is 21001202020177. The reversal of 21001202020121 is 12102020210012.

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 10799182736521 + 10202019283600 = 3286211^2 + 3194060^2 .

It is a cyclic number.

It is not a de Polignac number, because 21001202020121 - 2²⁶ = 21001134911257 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001202020096 and 21001202020105.

It is not an unprimeable number, because it can be changed into a prime (21001202020181) 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, 617682412340 + ... + 617682412373.

It is an arithmetic number, because the mean of its divisors is an integer number (5559141711213).

Almost surely, 2^{21001202020121} is an apocalyptic number.

It is an amenable number.

21001202020121 is a deficient number, since it is larger than the sum of its proper divisors (1235364824731).

21001202020121 is a wasteful number, since it uses less digits than its factorization.

21001202020121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1235364824730.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21001202020121 its reverse (12102020210012), we get a palindrome (33103222230133).

The spelling of 21001202020121 in words is "twenty-one trillion, one billion, two hundred two million, twenty thousand, one hundred twenty-one".