66666509 has 16 divisors (see below), whose sum is σ = 83731200. Its totient is φ = 52743600.

The previous prime is 66666493. The next prime is 66666517. The reversal of 66666509 is 90566666.

It is not a de Polignac number, because 66666509 - 2⁴ = 66666493 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 66666509.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66666559) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3017 + ... + 11934.

It is an arithmetic number, because the mean of its divisors is an integer number (5233200).

Almost surely, 2^66666509 is an apocalyptic number.

It is an amenable number.

66666509 is a deficient number, since it is larger than the sum of its proper divisors (17064691).

66666509 is a wasteful number, since it uses less digits than its factorization.

66666509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14985 (or 14971 counting only the distinct ones).

The product of its (nonzero) digits is 349920, while the sum is 44.

The square root of 66666509 is about 8164.9561541995. The cubic root of 66666509 is about 405.4798133845.

The spelling of 66666509 in words is "sixty-six million, six hundred sixty-six thousand, five hundred nine".