21212111220021 has 12 divisors (see below), whose sum is σ = 30808996409100. Its totient is φ = 14063278155840.

The previous prime is 21212111219987. The next prime is 21212111220031. The reversal of 21212111220021 is 12002211121212.

21212111220021 is a `hidden beast` number, since 212 + 1 + 211 + 1 + 220 + 0 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 2315832629796 + 18896278590225 = 1521786^2 + 4346985^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21212111220021 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21212111219976 and 21212111220003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212111220031) 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 11 ways as a sum of consecutive naturals, for example, 6510775296 + ... + 6510778553.

It is an arithmetic number, because the mean of its divisors is an integer number (2567416367425).

Almost surely, 2^{21212111220021} is an apocalyptic number.

It is an amenable number.

21212111220021 is a deficient number, since it is larger than the sum of its proper divisors (9596885189079).

21212111220021 is a wasteful number, since it uses less digits than its factorization.

21212111220021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13021554036 (or 13021554033 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

Adding to 21212111220021 its reverse (12002211121212), we get a palindrome (33214322341233).

The spelling of 21212111220021 in words is "twenty-one trillion, two hundred twelve billion, one hundred eleven million, two hundred twenty thousand, twenty-one".