866540209 has 2 divisors, whose sum is σ = 866540210. Its totient is φ = 866540208.

The previous prime is 866540189. The next prime is 866540221. The reversal of 866540209 is 902045668.

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., 777294400 + 89245809 = 27880^2 + 9447^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-866540209 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (866040209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 433270104 + 433270105.

It is an arithmetic number, because the mean of its divisors is an integer number (433270105).

Almost surely, 2^866540209 is an apocalyptic number.

It is an amenable number.

866540209 is a deficient number, since it is larger than the sum of its proper divisors (1).

866540209 is an equidigital number, since it uses as much as digits as its factorization.

866540209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 103680, while the sum is 40.

The square root of 866540209 is about 29437.0550327304. The cubic root of 866540209 is about 953.3731277367.

The spelling of 866540209 in words is "eight hundred sixty-six million, five hundred forty thousand, two hundred nine".