66688209 has 12 divisors (see below), whose sum is σ = 110088576. Its totient is φ = 38107512.

The previous prime is 66688207. The next prime is 66688211. The reversal of 66688209 is 90288666.

It is an interprime number because it is at equal distance from previous prime (66688207) and next prime (66688211).

It is not a de Polignac number, because 66688209 - 2¹ = 66688207 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66688207) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 529209 + ... + 529334.

It is an arithmetic number, because the mean of its divisors is an integer number (9174048).

Almost surely, 2^66688209 is an apocalyptic number.

It is an amenable number.

66688209 is a deficient number, since it is larger than the sum of its proper divisors (43400367).

66688209 is a wasteful number, since it uses less digits than its factorization.

66688209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1058556 (or 1058553 counting only the distinct ones).

The product of its (nonzero) digits is 248832, while the sum is 45.

The square root of 66688209 is about 8166.2848958385. The cubic root of 66688209 is about 405.5238032757.

The spelling of 66688209 in words is "sixty-six million, six hundred eighty-eight thousand, two hundred nine".