18101999 has 4 divisors (see below), whose sum is σ = 18110664. Its totient is φ = 18093336.

The previous prime is 18101971. The next prime is 18102013. The reversal of 18101999 is 99910181.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 18101999 - 2¹² = 18097903 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 (18101929) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 944 + ... + 6090.

It is an arithmetic number, because the mean of its divisors is an integer number (4527666).

Almost surely, 2^18101999 is an apocalyptic number.

18101999 is a deficient number, since it is larger than the sum of its proper divisors (8665).

18101999 is an equidigital number, since it uses as much as digits as its factorization.

18101999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8664.

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

The square root of 18101999 is about 4254.6444034725. The cubic root of 18101999 is about 262.5682313939.

The spelling of 18101999 in words is "eighteen million, one hundred one thousand, nine hundred ninety-nine".