21560565181 has 2 divisors, whose sum is σ = 21560565182. Its totient is φ = 21560565180.

The previous prime is 21560565179. The next prime is 21560565211. The reversal of 21560565181 is 18156506512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21172869081 + 387696100 = 145509^2 + 19690^2 .

It is a cyclic number.

It is not a de Polignac number, because 21560565181 - 2¹ = 21560565179 is a prime.

It is a super-2 number, since 2×21560565181² (a number of 21 digits) contains 22 as substring.

Together with 21560565179, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21560565581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10780282590 + 10780282591.

It is an arithmetic number, because the mean of its divisors is an integer number (10780282591).

Almost surely, 2^21560565181 is an apocalyptic number.

It is an amenable number.

21560565181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21560565181 is an equidigital number, since it uses as much as digits as its factorization.

21560565181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72000, while the sum is 40.

The spelling of 21560565181 in words is "twenty-one billion, five hundred sixty million, five hundred sixty-five thousand, one hundred eighty-one".