21581537519713 has 2 divisors, whose sum is σ = 21581537519714. Its totient is φ = 21581537519712.

The previous prime is 21581537519693. The next prime is 21581537519771. The reversal of 21581537519713 is 31791573518512.

It is an a-pointer prime, because the next prime (21581537519771) can be obtained adding 21581537519713 to its sum of digits (58).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18163893895744 + 3417643623969 = 4261912^2 + 1848687^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21581537519713 is a prime.

It is not a weakly prime, because it can be changed into another prime (21581537519513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10790768759856 + 10790768759857.

It is an arithmetic number, because the mean of its divisors is an integer number (10790768759857).

Almost surely, 2^{21581537519713} is an apocalyptic number.

It is an amenable number.

21581537519713 is a deficient number, since it is larger than the sum of its proper divisors (1).

21581537519713 is an equidigital number, since it uses as much as digits as its factorization.

21581537519713 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7938000, while the sum is 58.

The spelling of 21581537519713 in words is "twenty-one trillion, five hundred eighty-one billion, five hundred thirty-seven million, five hundred nineteen thousand, seven hundred thirteen".