18993891 has 24 divisors (see below), whose sum is σ = 29585920. Its totient is φ = 10616112.

The previous prime is 18993889. The next prime is 18993899. The reversal of 18993891 is 19839981.

It is not a de Polignac number, because 18993891 - 2¹ = 18993889 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18993891.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18993899) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 177460 + ... + 177566.

Almost surely, 2^18993891 is an apocalyptic number.

18993891 is a deficient number, since it is larger than the sum of its proper divisors (10592029).

18993891 is an equidigital number, since it uses as much as digits as its factorization.

18993891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 303 (or 196 counting only the distinct ones).

The product of its digits is 139968, while the sum is 48.

The square root of 18993891 is about 4358.1981368451. The cubic root of 18993891 is about 266.8115630949.

The spelling of 18993891 in words is "eighteen million, nine hundred ninety-three thousand, eight hundred ninety-one".