21010040021 has 2 divisors, whose sum is σ = 21010040022. Its totient is φ = 21010040020.

The previous prime is 21010040011. The next prime is 21010040057. The reversal of 21010040021 is 12004001012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14741359396 + 6268680625 = 121414^2 + 79175^2 .

It is a cyclic number.

It is not a de Polignac number, because 21010040021 - 2⁶ = 21010039957 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21010039984 and 21010040011.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21010040011) 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, 10505020010 + 10505020011.

It is an arithmetic number, because the mean of its divisors is an integer number (10505020011).

Almost surely, 2^21010040021 is an apocalyptic number.

It is an amenable number.

21010040021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21010040021 is an equidigital number, since it uses as much as digits as its factorization.

21010040021 is an odious number, because the sum of its binary digits is odd.

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

Adding to 21010040021 its reverse (12004001012), we get a palindrome (33014041033).

The spelling of 21010040021 in words is "twenty-one billion, ten million, forty thousand, twenty-one".