66666666666665 has 8 divisors (see below), whose sum is σ = 86153846153928. Its totient is φ = 49230769230720.

The previous prime is 66666666666647. The next prime is 66666666666737. The reversal of 66666666666665 is 56666666666666.

It can be written as a sum of positive squares in 4 ways, for example, as 1098958049344 + 65567708617321 = 1048312^2 + 8097389^2 .

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

It is not a de Polignac number, because 66666666666665 - 2¹² = 66666666662569 is a prime.

It is a super-4 number, since 4×66666666666665⁴ (a number of 56 digits) contains 4444 as substring.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 512820512756 + ... + 512820512885.

It is an arithmetic number, because the mean of its divisors is an integer number (10769230769241).

Almost surely, 2^{66666666666665} is an apocalyptic number.

66666666666665 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

66666666666665 is a deficient number, since it is larger than the sum of its proper divisors (19487179487263).

66666666666665 is a wasteful number, since it uses less digits than its factorization.

66666666666665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1025641025659.

The product of its digits is 65303470080, while the sum is 83.

Subtracting from 66666666666665 its reverse (56666666666666), we obtain a palindrome (9999999999999).

It can be divided in two parts, 6666666 and 6666665, that added together give a palindrome (13333331).

The spelling of 66666666666665 in words is "sixty-six trillion, six hundred sixty-six billion, six hundred sixty-six million, six hundred sixty-six thousand, six hundred sixty-five".