21010121212121 has 4 divisors (see below), whose sum is σ = 21734608150500. Its totient is φ = 20285634273744.

The previous prime is 21010121212109. The next prime is 21010121212169. The reversal of 21010121212121 is 12121212101012.

21010121212121 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.

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 8502327015625 + 12507794196496 = 2915875^2 + 3536636^2 .

It is a cyclic number.

It is not a de Polignac number, because 21010121212121 - 2¹⁸ = 21010120949977 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21010121212121.

It is not an unprimeable number, because it can be changed into a prime (21010121212721) 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, 362243469146 + ... + 362243469203.

It is an arithmetic number, because the mean of its divisors is an integer number (5433652037625).

Almost surely, 2^{21010121212121} is an apocalyptic number.

It is an amenable number.

21010121212121 is a deficient number, since it is larger than the sum of its proper divisors (724486938379).

21010121212121 is an equidigital number, since it uses as much as digits as its factorization.

21010121212121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724486938378.

The product of its (nonzero) digits is 32, while the sum is 17.

Adding to 21010121212121 its reverse (12121212101012), we get a palindrome (33131333313133).

It can be divided in two parts, 2101012 and 1212121, that added together give a palindrome (3313133).

The spelling of 21010121212121 in words is "twenty-one trillion, ten billion, one hundred twenty-one million, two hundred twelve thousand, one hundred twenty-one".