18991091 has 8 divisors (see below), whose sum is σ = 22980960. Its totient is φ = 15320448.

The previous prime is 18991081. The next prime is 18991117. The reversal of 18991091 is 19019981.

It is a happy number.

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 18991091 - 2¹⁰ = 18990067 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18991001) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 79676 + ... + 79913.

It is an arithmetic number, because the mean of its divisors is an integer number (2872620).

Almost surely, 2^18991091 is an apocalyptic number.

18991091 is a deficient number, since it is larger than the sum of its proper divisors (3989869).

18991091 is a wasteful number, since it uses less digits than its factorization.

18991091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159613.

The product of its (nonzero) digits is 5832, while the sum is 38.

The square root of 18991091 is about 4357.8768913314. The cubic root of 18991091 is about 266.7984517022.

The spelling of 18991091 in words is "eighteen million, nine hundred ninety-one thousand, ninety-one".