18391139 has 4 divisors (see below), whose sum is σ = 19805856. Its totient is φ = 16976424.

The previous prime is 18391129. The next prime is 18391151. The reversal of 18391139 is 93119381.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 18391139 - 2⁴ = 18391123 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 18391099 and 18391108.

It is not an unprimeable number, because it can be changed into a prime (18391129) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 707339 + ... + 707364.

It is an arithmetic number, because the mean of its divisors is an integer number (4951464).

Almost surely, 2^18391139 is an apocalyptic number.

18391139 is a deficient number, since it is larger than the sum of its proper divisors (1414717).

18391139 is a wasteful number, since it uses less digits than its factorization.

18391139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1414716.

The product of its digits is 5832, while the sum is 35.

The square root of 18391139 is about 4288.4891278864. The cubic root of 18391139 is about 263.9588386623.

The spelling of 18391139 in words is "eighteen million, three hundred ninety-one thousand, one hundred thirty-nine".