21765532513 has 2 divisors, whose sum is σ = 21765532514. Its totient is φ = 21765532512.

The previous prime is 21765532511. The next prime is 21765532567. The reversal of 21765532513 is 31523556712.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16717714209 + 5047818304 = 129297^2 + 71048^2 .

It is a cyclic number.

It is not a de Polignac number, because 21765532513 - 2¹ = 21765532511 is a prime.

Together with 21765532511, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21765532511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10882766256 + 10882766257.

It is an arithmetic number, because the mean of its divisors is an integer number (10882766257).

Almost surely, 2^21765532513 is an apocalyptic number.

It is an amenable number.

21765532513 is a deficient number, since it is larger than the sum of its proper divisors (1).

21765532513 is an equidigital number, since it uses as much as digits as its factorization.

21765532513 is an evil number, because the sum of its binary digits is even.

The product of its digits is 189000, while the sum is 40.

The spelling of 21765532513 in words is "twenty-one billion, seven hundred sixty-five million, five hundred thirty-two thousand, five hundred thirteen".