66409209 has 12 divisors (see below), whose sum is σ = 96168852. Its totient is φ = 44160000.

The previous prime is 66409201. The next prime is 66409267. The reversal of 66409209 is 90290466.

66409209 is a `hidden beast` number, since 6 + 640 + 9 + 2 + 0 + 9 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 52925625 + 13483584 = 7275^2 + 3672^2 .

It is not a de Polignac number, because 66409209 - 2³ = 66409201 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66409201) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 5592 + ... + 12809.

It is an arithmetic number, because the mean of its divisors is an integer number (8014071).

Almost surely, 2^66409209 is an apocalyptic number.

It is an amenable number.

66409209 is a deficient number, since it is larger than the sum of its proper divisors (29759643).

66409209 is a wasteful number, since it uses less digits than its factorization.

66409209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18808 (or 18805 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 36.

The square root of 66409209 is about 8149.1845604330. The cubic root of 66409209 is about 404.9574898226.

It can be divided in two parts, 6640920 and 9, that added together give a square (6640929 = 2577²).

The spelling of 66409209 in words is "sixty-six million, four hundred nine thousand, two hundred nine".