66565909 has 2 divisors, whose sum is σ = 66565910. Its totient is φ = 66565908.

The previous prime is 66565901. The next prime is 66565943. The reversal of 66565909 is 90956566.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 63600625 + 2965284 = 7975^2 + 1722^2 .

It is a cyclic number.

It is not a de Polignac number, because 66565909 - 2³ = 66565901 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66565901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33282954 + 33282955.

It is an arithmetic number, because the mean of its divisors is an integer number (33282955).

Almost surely, 2^66565909 is an apocalyptic number.

It is an amenable number.

66565909 is a deficient number, since it is larger than the sum of its proper divisors (1).

66565909 is an equidigital number, since it uses as much as digits as its factorization.

66565909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 437400, while the sum is 46.

The square root of 66565909 is about 8158.7933544122. The cubic root of 66565909 is about 405.2757538794.

The spelling of 66565909 in words is "sixty-six million, five hundred sixty-five thousand, nine hundred nine".