18918238 has 4 divisors (see below), whose sum is σ = 28377360. Its totient is φ = 9459118.

The previous prime is 18918233. The next prime is 18918253. The reversal of 18918238 is 83281981.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 83281981 = 59 ⋅1411559.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 18918238.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18918233) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4729558 + ... + 4729561.

It is an arithmetic number, because the mean of its divisors is an integer number (7094340).

Almost surely, 2^18918238 is an apocalyptic number.

18918238 is a deficient number, since it is larger than the sum of its proper divisors (9459122).

18918238 is an equidigital number, since it uses as much as digits as its factorization.

18918238 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9459121.

The product of its digits is 27648, while the sum is 40.

The square root of 18918238 is about 4349.5100873547. The cubic root of 18918238 is about 266.4568533650.

The spelling of 18918238 in words is "eighteen million, nine hundred eighteen thousand, two hundred thirty-eight".