66808909 has 2 divisors, whose sum is σ = 66808910. Its totient is φ = 66808908.

The previous prime is 66808891. The next prime is 66808913. The reversal of 66808909 is 90980866.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 63282025 + 3526884 = 7955^2 + 1878^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66808909 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66808919) 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, 33404454 + 33404455.

It is an arithmetic number, because the mean of its divisors is an integer number (33404455).

Almost surely, 2^66808909 is an apocalyptic number.

It is an amenable number.

66808909 is a deficient number, since it is larger than the sum of its proper divisors (1).

66808909 is an equidigital number, since it uses as much as digits as its factorization.

66808909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 186624, while the sum is 46.

The square root of 66808909 is about 8173.6716963676. The cubic root of 66808909 is about 405.7683103814.

The spelling of 66808909 in words is "sixty-six million, eight hundred eight thousand, nine hundred nine".