18991811 has 8 divisors (see below), whose sum is σ = 20233920. Its totient is φ = 17773992.

The previous prime is 18991793. The next prime is 18991831. The reversal of 18991811 is 11819981.

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

It is a cyclic number.

It is not a de Polignac number, because 18991811 - 2¹⁰ = 18990787 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18991831) 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, 4445 + ... + 7598.

It is an arithmetic number, because the mean of its divisors is an integer number (2529240).

Almost surely, 2^18991811 is an apocalyptic number.

18991811 is a deficient number, since it is larger than the sum of its proper divisors (1242109).

18991811 is a wasteful number, since it uses less digits than its factorization.

18991811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12145.

The product of its digits is 5184, while the sum is 38.

The square root of 18991811 is about 4357.9594995823. The cubic root of 18991811 is about 266.8018233262.

The spelling of 18991811 in words is "eighteen million, nine hundred ninety-one thousand, eight hundred eleven".