6645209 has 2 divisors, whose sum is σ = 6645210. Its totient is φ = 6645208.

The previous prime is 6645187. The next prime is 6645211. The reversal of 6645209 is 9025466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5784025 + 861184 = 2405^2 + 928^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6645209 is a prime.

It is a super-3 number, since 3×6645209³ (a number of 21 digits) contains 333 as substring.

Together with 6645211, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (6645259) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3322604 + 3322605.

It is an arithmetic number, because the mean of its divisors is an integer number (3322605).

Almost surely, 2^6645209 is an apocalyptic number.

It is an amenable number.

6645209 is a deficient number, since it is larger than the sum of its proper divisors (1).

6645209 is an equidigital number, since it uses as much as digits as its factorization.

6645209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 6645209 is about 2577.8302892161. The cubic root of 6645209 is about 188.0050643724.

The spelling of 6645209 in words is "six million, six hundred forty-five thousand, two hundred nine".