18666665 has 4 divisors (see below), whose sum is σ = 22400004. Its totient is φ = 14933328.

The previous prime is 18666647. The next prime is 18666667. The reversal of 18666665 is 56666681.

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

It can be written as a sum of positive squares in 2 ways, for example, as 5914624 + 12752041 = 2432^2 + 3571^2 .

It is a cyclic number.

It is not a de Polignac number, because 18666665 - 2²² = 14472361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18666667) 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, 1866662 + ... + 1866671.

It is an arithmetic number, because the mean of its divisors is an integer number (5600001).

Almost surely, 2^18666665 is an apocalyptic number.

It is an amenable number.

18666665 is a deficient number, since it is larger than the sum of its proper divisors (3733339).

18666665 is an equidigital number, since it uses as much as digits as its factorization.

18666665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3733338.

The product of its digits is 311040, while the sum is 44.

The square root of 18666665 is about 4320.4936060594. The cubic root of 18666665 is about 265.2704726315.

The spelling of 18666665 in words is "eighteen million, six hundred sixty-six thousand, six hundred sixty-five".