66809665 has 8 divisors (see below), whose sum is σ = 86338728. Its totient is φ = 49336320.

The previous prime is 66809599. The next prime is 66809671. The reversal of 66809665 is 56690866.

It can be written as a sum of positive squares in 4 ways, for example, as 2745649 + 64064016 = 1657^2 + 8004^2 .

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

It is not a de Polignac number, because 66809665 - 2⁹ = 66809153 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 513856 + ... + 513985.

It is an arithmetic number, because the mean of its divisors is an integer number (10792341).

Almost surely, 2^66809665 is an apocalyptic number.

66809665 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

66809665 is a deficient number, since it is larger than the sum of its proper divisors (19529063).

66809665 is a wasteful number, since it uses less digits than its factorization.

66809665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1027859.

The product of its (nonzero) digits is 466560, while the sum is 46.

The square root of 66809665 is about 8173.7179422831. The cubic root of 66809665 is about 405.7698409143.

The spelling of 66809665 in words is "sixty-six million, eight hundred nine thousand, six hundred sixty-five".