21012442021 has 2 divisors, whose sum is σ = 21012442022. Its totient is φ = 21012442020.

The previous prime is 21012442001. The next prime is 21012442027. The reversal of 21012442021 is 12024421012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18601140996 + 2411301025 = 136386^2 + 49105^2 .

It is a cyclic number.

It is not a de Polignac number, because 21012442021 - 2³³ = 12422507429 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21012442021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21012442027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10506221010 + 10506221011.

It is an arithmetic number, because the mean of its divisors is an integer number (10506221011).

Almost surely, 2^21012442021 is an apocalyptic number.

It is an amenable number.

21012442021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21012442021 is an equidigital number, since it uses as much as digits as its factorization.

21012442021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 256, while the sum is 19.

Adding to 21012442021 its reverse (12024421012), we get a palindrome (33036863033).

The spelling of 21012442021 in words is "twenty-one billion, twelve million, four hundred forty-two thousand, twenty-one".