21002321521 has 2 divisors, whose sum is σ = 21002321522. Its totient is φ = 21002321520.

The previous prime is 21002321497. The next prime is 21002321531. The reversal of 21002321521 is 12512320012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18404992225 + 2597329296 = 135665^2 + 50964^2 .

It is a cyclic number.

It is not a de Polignac number, because 21002321521 - 2⁷ = 21002321393 is a prime.

It is not a weakly prime, because it can be changed into another prime (21002321531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501160760 + 10501160761.

It is an arithmetic number, because the mean of its divisors is an integer number (10501160761).

Almost surely, 2^21002321521 is an apocalyptic number.

It is an amenable number.

21002321521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002321521 is an equidigital number, since it uses as much as digits as its factorization.

21002321521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 240, while the sum is 19.

Adding to 21002321521 its reverse (12512320012), we get a palindrome (33514641533).

The spelling of 21002321521 in words is "twenty-one billion, two million, three hundred twenty-one thousand, five hundred twenty-one".