18115666 has 4 divisors (see below), whose sum is σ = 27173502. Its totient is φ = 9057832.

The previous prime is 18115639. The next prime is 18115667. The reversal of 18115666 is 66651181.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 66651181 = 2371 ⋅28111.

It can be written as a sum of positive squares in only one way, i.e., 14600041 + 3515625 = 3821^2 + 1875^2 .

It is not an unprimeable number, because it can be changed into a prime (18115667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4528915 + ... + 4528918.

Almost surely, 2^18115666 is an apocalyptic number.

18115666 is a deficient number, since it is larger than the sum of its proper divisors (9057836).

18115666 is an equidigital number, since it uses as much as digits as its factorization.

18115666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9057835.

The product of its digits is 8640, while the sum is 34.

The square root of 18115666 is about 4256.2502276065. The cubic root of 18115666 is about 262.6342943977.

It can be divided in two parts, 18115 and 666, that added together give a palindrome (18781).

The spelling of 18115666 in words is "eighteen million, one hundred fifteen thousand, six hundred sixty-six".