18918491 has 4 divisors (see below), whose sum is σ = 18928800. Its totient is φ = 18908184.

The previous prime is 18918457. The next prime is 18918499. The reversal of 18918491 is 19481981.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 18918491 - 2¹⁰ = 18917467 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18918499) 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 3 ways as a sum of consecutive naturals, for example, 1571 + ... + 6348.

It is an arithmetic number, because the mean of its divisors is an integer number (4732200).

Almost surely, 2^18918491 is an apocalyptic number.

18918491 is a deficient number, since it is larger than the sum of its proper divisors (10309).

18918491 is an equidigital number, since it uses as much as digits as its factorization.

18918491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10308.

The product of its digits is 20736, while the sum is 41.

The square root of 18918491 is about 4349.5391709927. The cubic root of 18918491 is about 266.4580411656.

The spelling of 18918491 in words is "eighteen million, nine hundred eighteen thousand, four hundred ninety-one".