21121022100221 has 4 divisors (see below), whose sum is σ = 21166837766844. Its totient is φ = 21075206433600.

The previous prime is 21121022100209. The next prime is 21121022100239. The reversal of 21121022100221 is 12200122012112.

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 8722778299225 + 12398243800996 = 2953435^2 + 3521114^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21121022100221 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 21121022100221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121022100271) 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, 22907832620 + ... + 22907833541.

It is an arithmetic number, because the mean of its divisors is an integer number (5291709441711).

Almost surely, 2^{21121022100221} is an apocalyptic number.

It is an amenable number.

21121022100221 is a deficient number, since it is larger than the sum of its proper divisors (45815666623).

21121022100221 is an equidigital number, since it uses as much as digits as its factorization.

21121022100221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45815666622.

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

Adding to 21121022100221 its reverse (12200122012112), we get a palindrome (33321144112333).

The spelling of 21121022100221 in words is "twenty-one trillion, one hundred twenty-one billion, twenty-two million, one hundred thousand, two hundred twenty-one".