66520009 has 4 divisors (see below), whose sum is σ = 67431316. Its totient is φ = 65608704.

The previous prime is 66520001. The next prime is 66520039. The reversal of 66520009 is 90002566.

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 32262400 + 34257609 = 5680^2 + 5853^2 .

It is a cyclic number.

It is not a de Polignac number, because 66520009 - 2³ = 66520001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66520001) 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, 455544 + ... + 455689.

It is an arithmetic number, because the mean of its divisors is an integer number (16857829).

Almost surely, 2^66520009 is an apocalyptic number.

It is an amenable number.

66520009 is a deficient number, since it is larger than the sum of its proper divisors (911307).

66520009 is an equidigital number, since it uses as much as digits as its factorization.

66520009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 911306.

The product of its (nonzero) digits is 3240, while the sum is 28.

The square root of 66520009 is about 8155.9799533839. The cubic root of 66520009 is about 405.1825808890.

The spelling of 66520009 in words is "sixty-six million, five hundred twenty thousand, nine".