18090991 has 4 divisors (see below), whose sum is σ = 18105952. Its totient is φ = 18076032.

The previous prime is 18090979. The next prime is 18090997. The reversal of 18090991 is 19909081.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 18090991 - 2⁵ = 18090959 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18090991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18090997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5490 + ... + 8143.

It is an arithmetic number, because the mean of its divisors is an integer number (4526488).

Almost surely, 2^18090991 is an apocalyptic number.

18090991 is a deficient number, since it is larger than the sum of its proper divisors (14961).

18090991 is a wasteful number, since it uses less digits than its factorization.

18090991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14960.

The product of its (nonzero) digits is 5832, while the sum is 37.

The square root of 18090991 is about 4253.3505616161. The cubic root of 18090991 is about 262.5149971779.

The spelling of 18090991 in words is "eighteen million, ninety thousand, nine hundred ninety-one".