21100121211221 has 4 divisors (see below), whose sum is σ = 22723207458252. Its totient is φ = 19477034964192.

The previous prime is 21100121211217. The next prime is 21100121211263. The reversal of 21100121211221 is 12211212100112.

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 4798351584196 + 16301769627025 = 2190514^2 + 4037545^2 .

It is not a de Polignac number, because 21100121211221 - 2² = 21100121211217 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 21100121211221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21100121210221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 811543123496 + ... + 811543123521.

It is an arithmetic number, because the mean of its divisors is an integer number (5680801864563).

Almost surely, 2^{21100121211221} is an apocalyptic number.

It is an amenable number.

21100121211221 is a deficient number, since it is larger than the sum of its proper divisors (1623086247031).

21100121211221 is a wasteful number, since it uses less digits than its factorization.

21100121211221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1623086247030.

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

Adding to 21100121211221 its reverse (12211212100112), we get a palindrome (33311333311333).

It can be divided in two parts, 2110012 and 1211221, that added together give a palindrome (3321233).

The spelling of 21100121211221 in words is "twenty-one trillion, one hundred billion, one hundred twenty-one million, two hundred eleven thousand, two hundred twenty-one".