21012221200021 has 2 divisors, whose sum is σ = 21012221200022. Its totient is φ = 21012221200020.

The previous prime is 21012221199979. The next prime is 21012221200051. The reversal of 21012221200021 is 12000212221012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20286511443025 + 725709756996 = 4504055^2 + 851886^2 .

It is a cyclic number.

It is not a de Polignac number, because 21012221200021 - 2¹¹ = 21012221197973 is a prime.

It is a super-2 number, since 2×21012221200021² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21012221199968 and 21012221200004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21012221200051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10506110600010 + 10506110600011.

It is an arithmetic number, because the mean of its divisors is an integer number (10506110600011).

Almost surely, 2^{21012221200021} is an apocalyptic number.

It is an amenable number.

21012221200021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21012221200021 is an equidigital number, since it uses as much as digits as its factorization.

21012221200021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21012221200021 its reverse (12000212221012), we get a palindrome (33012433421033).

The spelling of 21012221200021 in words is "twenty-one trillion, twelve billion, two hundred twenty-one million, two hundred thousand, twenty-one".