18985555345621 has 2 divisors, whose sum is σ = 18985555345622. Its totient is φ = 18985555345620.

The previous prime is 18985555345591. The next prime is 18985555345637. The reversal of 18985555345621 is 12654355558981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18246686164996 + 738869180625 = 4271614^2 + 859575^2 .

It is an emirp because it is prime and its reverse (12654355558981) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18985555345621 - 2¹⁵ = 18985555312853 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18985555345651) 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, 9492777672810 + 9492777672811.

It is an arithmetic number, because the mean of its divisors is an integer number (9492777672811).

Almost surely, 2^{18985555345621} is an apocalyptic number.

It is an amenable number.

18985555345621 is a deficient number, since it is larger than the sum of its proper divisors (1).

18985555345621 is an equidigital number, since it uses as much as digits as its factorization.

18985555345621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 259200000, while the sum is 67.

The spelling of 18985555345621 in words is "eighteen trillion, nine hundred eighty-five billion, five hundred fifty-five million, three hundred forty-five thousand, six hundred twenty-one".