21210220100021 has 2 divisors, whose sum is σ = 21210220100022. Its totient is φ = 21210220100020.

The previous prime is 21210220100009. The next prime is 21210220100023. The reversal of 21210220100021 is 12000102201212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13661051719396 + 7549168380625 = 3696086^2 + 2747575^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210220100021 - 2³⁴ = 21193040230837 is a prime.

Together with 21210220100023, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21210220099969 and 21210220100005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21210220100023) 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 as a sum of consecutive naturals, namely, 10605110050010 + 10605110050011.

It is an arithmetic number, because the mean of its divisors is an integer number (10605110050011).

Almost surely, 2^{21210220100021} is an apocalyptic number.

It is an amenable number.

21210220100021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210220100021 is an equidigital number, since it uses as much as digits as its factorization.

21210220100021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21210220100021 its reverse (12000102201212), we get a palindrome (33210322301233).

The spelling of 21210220100021 in words is "twenty-one trillion, two hundred ten billion, two hundred twenty million, one hundred thousand, twenty-one".