21010123021 has 2 divisors, whose sum is σ = 21010123022. Its totient is φ = 21010123020.

The previous prime is 21010123019. The next prime is 21010123033. The reversal of 21010123021 is 12032101012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18882607396 + 2127515625 = 137414^2 + 46125^2 .

It is a cyclic number.

It is not a de Polignac number, because 21010123021 - 2¹ = 21010123019 is a prime.

Together with 21010123019, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21010122992 and 21010123010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21010123091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505061510 + 10505061511.

It is an arithmetic number, because the mean of its divisors is an integer number (10505061511).

Almost surely, 2^21010123021 is an apocalyptic number.

It is an amenable number.

21010123021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21010123021 is an equidigital number, since it uses as much as digits as its factorization.

21010123021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24, while the sum is 13.

Adding to 21010123021 its reverse (12032101012), we get a palindrome (33042224033).

The spelling of 21010123021 in words is "twenty-one billion, ten million, one hundred twenty-three thousand, twenty-one".