18181566553 has 2 divisors, whose sum is σ = 18181566554. Its totient is φ = 18181566552.

The previous prime is 18181566551. The next prime is 18181566569. The reversal of 18181566553 is 35566518181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9117003289 + 9064563264 = 95483^2 + 95208^2 .

It is an emirp because it is prime and its reverse (35566518181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18181566553 - 2¹ = 18181566551 is a prime.

Together with 18181566551, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 18181566497 and 18181566506.

It is not a weakly prime, because it can be changed into another prime (18181566551) 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, 9090783276 + 9090783277.

It is an arithmetic number, because the mean of its divisors is an integer number (9090783277).

Almost surely, 2^18181566553 is an apocalyptic number.

It is an amenable number.

18181566553 is a deficient number, since it is larger than the sum of its proper divisors (1).

18181566553 is an equidigital number, since it uses as much as digits as its factorization.

18181566553 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864000, while the sum is 49.

The spelling of 18181566553 in words is "eighteen billion, one hundred eighty-one million, five hundred sixty-six thousand, five hundred fifty-three".