21212000021 has 2 divisors, whose sum is σ = 21212000022. Its totient is φ = 21212000020.

The previous prime is 21211999979. The next prime is 21212000027. The reversal of 21212000021 is 12000021212.

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., 20860024900 + 351975121 = 144430^2 + 18761^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21212000021 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21211999966 and 21212000011.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21212000027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606000010 + 10606000011.

It is an arithmetic number, because the mean of its divisors is an integer number (10606000011).

Almost surely, 2^21212000021 is an apocalyptic number.

It is an amenable number.

21212000021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212000021 is an equidigital number, since it uses as much as digits as its factorization.

21212000021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21212000021 its reverse (12000021212), we get a palindrome (33212021233).

It can be divided in two parts, 212 and 12000021, that multiplied together give a palindrome (2544004452).

The spelling of 21212000021 in words is "twenty-one billion, two hundred twelve million, twenty-one", and thus it is an aban number.