18127991 has 6 divisors (see below), whose sum is σ = 21087720. Its totient is φ = 15538236.

The previous prime is 18127981. The next prime is 18127997. The reversal of 18127991 is 19972181.

It is a de Polignac number, because none of the positive numbers 2^k-18127991 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 (18127997) 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 5 ways as a sum of consecutive naturals, for example, 184931 + ... + 185028.

It is an arithmetic number, because the mean of its divisors is an integer number (3514620).

Almost surely, 2^18127991 is an apocalyptic number.

18127991 is a deficient number, since it is larger than the sum of its proper divisors (2959729).

18127991 is an equidigital number, since it uses as much as digits as its factorization.

18127991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 369973 (or 369966 counting only the distinct ones).

The product of its digits is 9072, while the sum is 38.

The square root of 18127991 is about 4257.6978521262. The cubic root of 18127991 is about 262.6938420081.

The spelling of 18127991 in words is "eighteen million, one hundred twenty-seven thousand, nine hundred ninety-one".