18381218549 has 2 divisors, whose sum is σ = 18381218550. Its totient is φ = 18381218548.

The previous prime is 18381218539. The next prime is 18381218551. The reversal of 18381218549 is 94581218381.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16797974449 + 1583244100 = 129607^2 + 39790^2 .

It is a cyclic number.

It is not a de Polignac number, because 18381218549 - 2⁸ = 18381218293 is a prime.

It is a super-2 number, since 2×18381218549² (a number of 21 digits) contains 22 as substring.

Together with 18381218551, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between odd and even.

It is a junction number, because it is equal to n+sod(n) for n = 18381218497 and 18381218506.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18381218539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9190609274 + 9190609275.

It is an arithmetic number, because the mean of its divisors is an integer number (9190609275).

Almost surely, 2^18381218549 is an apocalyptic number.

It is an amenable number.

18381218549 is a deficient number, since it is larger than the sum of its proper divisors (1).

18381218549 is an equidigital number, since it uses as much as digits as its factorization.

18381218549 is an evil number, because the sum of its binary digits is even.

The product of its digits is 552960, while the sum is 50.

The spelling of 18381218549 in words is "eighteen billion, three hundred eighty-one million, two hundred eighteen thousand, five hundred forty-nine".