18043991 has 8 divisors (see below), whose sum is σ = 20685600. Its totient is φ = 15418368.

The previous prime is 18043981. The next prime is 18043997. The reversal of 18043991 is 19934081.

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

It is not a de Polignac number, because 18043991 - 2²² = 13849687 is a prime.

It is a super-2 number, since 2×18043991² = 651171222416162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18043997) 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, 1466 + ... + 6183.

It is an arithmetic number, because the mean of its divisors is an integer number (2585700).

Almost surely, 2^18043991 is an apocalyptic number.

18043991 is a deficient number, since it is larger than the sum of its proper divisors (2641609).

18043991 is an equidigital number, since it uses as much as digits as its factorization.

18043991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7993.

The product of its (nonzero) digits is 7776, while the sum is 35.

The square root of 18043991 is about 4247.8219124629. The cubic root of 18043991 is about 262.2874639431.

The spelling of 18043991 in words is "eighteen million, forty-three thousand, nine hundred ninety-one".