6666509 has 2 divisors, whose sum is σ = 6666510. Its totient is φ = 6666508.

The previous prime is 6666487. The next prime is 6666523. The reversal of 6666509 is 9056666.

6666509 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 4937284 + 1729225 = 2222^2 + 1315^2 .

It is a cyclic number.

It is not a de Polignac number, because 6666509 - 2²⁰ = 5617933 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6666589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3333254 + 3333255.

It is an arithmetic number, because the mean of its divisors is an integer number (3333255).

Almost surely, 2^6666509 is an apocalyptic number.

It is an amenable number.

6666509 is a deficient number, since it is larger than the sum of its proper divisors (1).

6666509 is an equidigital number, since it uses as much as digits as its factorization.

6666509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 58320, while the sum is 38.

The square root of 6666509 is about 2581.9583652724. The cubic root of 6666509 is about 188.2057220644.

The spelling of 6666509 in words is "six million, six hundred sixty-six thousand, five hundred nine".