18991338 has 8 divisors (see below), whose sum is σ = 37982688. Its totient is φ = 6330444.

The previous prime is 18991319. The next prime is 18991361. The reversal of 18991338 is 83319981.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

18991338 is an admirable number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 18991338.

It is an unprimeable number.

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, 1582606 + ... + 1582617.

It is an arithmetic number, because the mean of its divisors is an integer number (4747836).

Almost surely, 2^18991338 is an apocalyptic number.

18991338 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18991338 is a wasteful number, since it uses less digits than its factorization.

18991338 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3165228.

The product of its digits is 46656, while the sum is 42.

The square root of 18991338 is about 4357.9052307273. The cubic root of 18991338 is about 266.7996083662.

The spelling of 18991338 in words is "eighteen million, nine hundred ninety-one thousand, three hundred thirty-eight".