21300011561 has 2 divisors, whose sum is σ = 21300011562. Its totient is φ = 21300011560.

The previous prime is 21300011543. The next prime is 21300011563. The reversal of 21300011561 is 16511000312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21270472336 + 29539225 = 145844^2 + 5435^2 .

It is a cyclic number.

It is not a de Polignac number, because 21300011561 - 2⁶ = 21300011497 is a prime.

Together with 21300011563, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21300011563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10650005780 + 10650005781.

It is an arithmetic number, because the mean of its divisors is an integer number (10650005781).

Almost surely, 2^21300011561 is an apocalyptic number.

It is an amenable number.

21300011561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21300011561 is an equidigital number, since it uses as much as digits as its factorization.

21300011561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 180, while the sum is 20.

Adding to 21300011561 its reverse (16511000312), we get a palindrome (37811011873).

The spelling of 21300011561 in words is "twenty-one billion, three hundred million, eleven thousand, five hundred sixty-one".