18904993 has 8 divisors (see below), whose sum is σ = 19581408. Its totient is φ = 18239424.

The previous prime is 18904987. The next prime is 18904997. The reversal of 18904993 is 39940981.

18904993 is nontrivially palindromic in base 13.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18904993 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (43).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18904997) 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 7 ways as a sum of consecutive naturals, for example, 921 + ... + 6217.

It is an arithmetic number, because the mean of its divisors is an integer number (2447676).

Almost surely, 2^18904993 is an apocalyptic number.

It is an amenable number.

18904993 is a deficient number, since it is larger than the sum of its proper divisors (676415).

18904993 is an equidigital number, since it uses as much as digits as its factorization.

18904993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5423.

The product of its (nonzero) digits is 69984, while the sum is 43.

The square root of 18904993 is about 4347.9872354918. The cubic root of 18904993 is about 266.3946550960.

The spelling of 18904993 in words is "eighteen million, nine hundred four thousand, nine hundred ninety-three".