18166399 has 4 divisors (see below), whose sum is σ = 18175264. Its totient is φ = 18157536.

The previous prime is 18166397. The next prime is 18166429. The reversal of 18166399 is 99366181.

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, and also an emirpimes, since its reverse is a distinct semiprime: 99366181 = 19 ⋅5229799.

It is a cyclic number.

It is not a de Polignac number, because 18166399 - 2¹ = 18166397 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 (18166391) 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, 394 + ... + 6040.

It is an arithmetic number, because the mean of its divisors is an integer number (4543816).

Almost surely, 2^18166399 is an apocalyptic number.

18166399 is a deficient number, since it is larger than the sum of its proper divisors (8865).

18166399 is an equidigital number, since it uses as much as digits as its factorization.

18166399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8864.

The product of its digits is 69984, while the sum is 43.

The square root of 18166399 is about 4262.2058842810. The cubic root of 18166399 is about 262.8792353748.

The spelling of 18166399 in words is "eighteen million, one hundred sixty-six thousand, three hundred ninety-nine".