21001112212121 has 4 divisors (see below), whose sum is σ = 21001121523492. Its totient is φ = 21001102900752.

The previous prime is 21001112212099. The next prime is 21001112212139. The reversal of 21001112212121 is 12121221110012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 10830753402121 + 10170358810000 = 3291011^2 + 3189100^2 .

It is a cyclic number.

It is not a de Polignac number, because 21001112212121 - 2¹⁰ = 21001112211097 is a prime.

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 21001112212121.

It is not an unprimeable number, because it can be changed into a prime (21001112412121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1096115 + ... + 6572951.

It is an arithmetic number, because the mean of its divisors is an integer number (5250280380873).

Almost surely, 2^{21001112212121} is an apocalyptic number.

It is an amenable number.

21001112212121 is a deficient number, since it is larger than the sum of its proper divisors (9311371).

21001112212121 is an equidigital number, since it uses as much as digits as its factorization.

21001112212121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9311370.

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

Adding to 21001112212121 its reverse (12121221110012), we get a palindrome (33122333322133).

The spelling of 21001112212121 in words is "twenty-one trillion, one billion, one hundred twelve million, two hundred twelve thousand, one hundred twenty-one".