21102120212221 has 4 divisors (see below), whose sum is σ = 21189680877244. Its totient is φ = 21014559547200.

The previous prime is 21102120212219. The next prime is 21102120212267. The reversal of 21102120212221 is 12221202120112.

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 19591644800025 + 1510475412196 = 4426245^2 + 1229014^2 .

It is a cyclic number.

It is not a de Polignac number, because 21102120212221 - 2¹ = 21102120212219 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21102120212021) 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, 43780332150 + ... + 43780332631.

It is an arithmetic number, because the mean of its divisors is an integer number (5297420219311).

Almost surely, 2^{21102120212221} is an apocalyptic number.

It is an amenable number.

21102120212221 is a deficient number, since it is larger than the sum of its proper divisors (87560665023).

21102120212221 is an equidigital number, since it uses as much as digits as its factorization.

21102120212221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87560665022.

The product of its (nonzero) digits is 128, while the sum is 19.

Adding to 21102120212221 its reverse (12221202120112), we get a palindrome (33323322332333).

The spelling of 21102120212221 in words is "twenty-one trillion, one hundred two billion, one hundred twenty million, two hundred twelve thousand, two hundred twenty-one".