18201999 has 4 divisors (see below), whose sum is σ = 24269336. Its totient is φ = 12134664.

The previous prime is 18201979. The next prime is 18202003. The reversal of 18201999 is 99910281.

It is a happy number.

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

It is not a de Polignac number, because 18201999 - 2¹⁶ = 18136463 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 (18201959) 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, 3033664 + ... + 3033669.

It is an arithmetic number, because the mean of its divisors is an integer number (6067334).

Almost surely, 2^18201999 is an apocalyptic number.

18201999 is a deficient number, since it is larger than the sum of its proper divisors (6067337).

18201999 is an equidigital number, since it uses as much as digits as its factorization.

18201999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6067336.

The product of its (nonzero) digits is 11664, while the sum is 39.

The square root of 18201999 is about 4266.3800815211. The cubic root of 18201999 is about 263.0508414676.

The spelling of 18201999 in words is "eighteen million, two hundred one thousand, nine hundred ninety-nine".