21200212120121 has 4 divisors (see below), whose sum is σ = 21200227958772. Its totient is φ = 21200196281472.

The previous prime is 21200212120099. The next prime is 21200212120181. The reversal of 21200212120121 is 12102121200212.

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 15801857274025 + 5398354846096 = 3975155^2 + 2323436^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21200212120121 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 21200212120121.

It is not an unprimeable number, because it can be changed into a prime (21200212120181) 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, 5705216 + ... + 8657361.

It is an arithmetic number, because the mean of its divisors is an integer number (5300056989693).

Almost surely, 2^{21200212120121} is an apocalyptic number.

It is an amenable number.

21200212120121 is a deficient number, since it is larger than the sum of its proper divisors (15838651).

21200212120121 is a wasteful number, since it uses less digits than its factorization.

21200212120121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15838650.

The product of its (nonzero) digits is 64, while the sum is 17.

Adding to 21200212120121 its reverse (12102121200212), we get a palindrome (33302333320333).

The spelling of 21200212120121 in words is "twenty-one trillion, two hundred billion, two hundred twelve million, one hundred twenty thousand, one hundred twenty-one".