66780209 has 2 divisors, whose sum is σ = 66780210. Its totient is φ = 66780208.

The previous prime is 66780151. The next prime is 66780211. The reversal of 66780209 is 90208766.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 40360609 + 26419600 = 6353^2 + 5140^2 .

It is a cyclic number.

It is not a de Polignac number, because 66780209 - 2¹⁶ = 66714673 is a prime.

It is a Sophie Germain prime.

Together with 66780211, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (66780289) 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 as a sum of consecutive naturals, namely, 33390104 + 33390105.

It is an arithmetic number, because the mean of its divisors is an integer number (33390105).

Almost surely, 2^66780209 is an apocalyptic number.

It is an amenable number.

66780209 is a deficient number, since it is larger than the sum of its proper divisors (1).

66780209 is an equidigital number, since it uses as much as digits as its factorization.

66780209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36288, while the sum is 38.

The square root of 66780209 is about 8171.9158708347. The cubic root of 66780209 is about 405.7101982790.

The spelling of 66780209 in words is "sixty-six million, seven hundred eighty thousand, two hundred nine".