66666689 has 4 divisors (see below), whose sum is σ = 67278420. Its totient is φ = 66054960.

The previous prime is 66666683. The next prime is 66666713. The reversal of 66666689 is 98666666.

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 33408400 + 33258289 = 5780^2 + 5767^2 .

It is a cyclic number.

It is not a de Polignac number, because 66666689 - 2⁸ = 66666433 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 10.

It is a zygodrome in base 3.

It is a self number, because there is not a number n which added to its sum of digits gives 66666689.

It is not an unprimeable number, because it can be changed into a prime (66666683) 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, 305702 + ... + 305919.

It is an arithmetic number, because the mean of its divisors is an integer number (16819605).

Almost surely, 2^66666689 is an apocalyptic number.

It is an amenable number.

66666689 is a deficient number, since it is larger than the sum of its proper divisors (611731).

66666689 is a wasteful number, since it uses less digits than its factorization.

66666689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 611730.

The product of its digits is 3359232, while the sum is 53.

The square root of 66666689 is about 8164.9671769089. The cubic root of 66666689 is about 405.4801783168.

The spelling of 66666689 in words is "sixty-six million, six hundred sixty-six thousand, six hundred eighty-nine".