66666665 has 8 divisors (see below), whose sum is σ = 86153928. Its totient is φ = 49230720.

The previous prime is 66666653. The next prime is 66666667. The reversal of 66666665 is 56666666.

66666665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 1315609 + 65351056 = 1147^2 + 8084^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 66666665 - 2⁸ = 66666409 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (66666667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 512756 + ... + 512885.

It is an arithmetic number, because the mean of its divisors is an integer number (10769241).

Almost surely, 2^66666665 is an apocalyptic number.

66666665 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

66666665 is a deficient number, since it is larger than the sum of its proper divisors (19487263).

66666665 is a wasteful number, since it uses less digits than its factorization.

66666665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1025659.

The product of its digits is 1399680, while the sum is 47.

The square root of 66666665 is about 8164.9657072152. The cubic root of 66666665 is about 405.4801296592.

Subtracting from 66666665 its reverse (56666666), we obtain a palindrome (9999999).

It can be divided in two parts, 6666 and 6665, that added together give a palindrome (13331).

The spelling of 66666665 in words is "sixty-six million, six hundred sixty-six thousand, six hundred sixty-five".