18138509 has 2 divisors, whose sum is σ = 18138510. Its totient is φ = 18138508.

The previous prime is 18138499. The next prime is 18138511. The reversal of 18138509 is 90583181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17197609 + 940900 = 4147^2 + 970^2 .

It is a cyclic number.

It is not a de Polignac number, because 18138509 - 2⁴ = 18138493 is a prime.

Together with 18138511, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18138539) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9069254 + 9069255.

It is an arithmetic number, because the mean of its divisors is an integer number (9069255).

Almost surely, 2^18138509 is an apocalyptic number.

It is an amenable number.

18138509 is a deficient number, since it is larger than the sum of its proper divisors (1).

18138509 is an equidigital number, since it uses as much as digits as its factorization.

18138509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8640, while the sum is 35.

The square root of 18138509 is about 4258.9328475570. The cubic root of 18138509 is about 262.7446378488.

The spelling of 18138509 in words is "eighteen million, one hundred thirty-eight thousand, five hundred nine".