18381818209 has 2 divisors, whose sum is σ = 18381818210. Its totient is φ = 18381818208.

The previous prime is 18381818167. The next prime is 18381818239. The reversal of 18381818209 is 90281818381.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15620000400 + 2761817809 = 124980^2 + 52553^2 .

It is an emirp because it is prime and its reverse (90281818381) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18381818209 - 2¹¹ = 18381816161 is a prime.

It is not a weakly prime, because it can be changed into another prime (18381818239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9190909104 + 9190909105.

It is an arithmetic number, because the mean of its divisors is an integer number (9190909105).

Almost surely, 2^18381818209 is an apocalyptic number.

It is an amenable number.

18381818209 is a deficient number, since it is larger than the sum of its proper divisors (1).

18381818209 is an equidigital number, since it uses as much as digits as its factorization.

18381818209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 221184, while the sum is 49.

The spelling of 18381818209 in words is "eighteen billion, three hundred eighty-one million, eight hundred eighteen thousand, two hundred nine".