18159991 has 8 divisors (see below), whose sum is σ = 19379120. Its totient is φ = 16967232.

The previous prime is 18159989. The next prime is 18160013. The reversal of 18159991 is 19995181.

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 18159991 - 2¹ = 18159989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18159941) 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 7 ways as a sum of consecutive naturals, for example, 5160 + ... + 7933.

It is an arithmetic number, because the mean of its divisors is an integer number (2422390).

Almost surely, 2^18159991 is an apocalyptic number.

18159991 is a deficient number, since it is larger than the sum of its proper divisors (1219129).

18159991 is a wasteful number, since it uses less digits than its factorization.

18159991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13185.

The product of its digits is 29160, while the sum is 43.

The square root of 18159991 is about 4261.4540945550. The cubic root of 18159991 is about 262.8483224744.

The spelling of 18159991 in words is "eighteen million, one hundred fifty-nine thousand, nine hundred ninety-one".