18138391 has 4 divisors (see below), whose sum is σ = 18276984. Its totient is φ = 17999800.

The previous prime is 18138361. The next prime is 18138397. The reversal of 18138391 is 19383181.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19383181 = 23 ⋅842747.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18138391 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18138397) 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 in 3 ways as a sum of consecutive naturals, for example, 69100 + ... + 69361.

It is an arithmetic number, because the mean of its divisors is an integer number (4569246).

Almost surely, 2^18138391 is an apocalyptic number.

18138391 is a deficient number, since it is larger than the sum of its proper divisors (138593).

18138391 is a wasteful number, since it uses less digits than its factorization.

18138391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138592.

The product of its digits is 5184, while the sum is 34.

The square root of 18138391 is about 4258.9189942989. The cubic root of 18138391 is about 262.7440680862.

The spelling of 18138391 in words is "eighteen million, one hundred thirty-eight thousand, three hundred ninety-one".