866509307221 has 2 divisors, whose sum is σ = 866509307222. Its totient is φ = 866509307220.

The previous prime is 866509307179. The next prime is 866509307239. The reversal of 866509307221 is 122703905668.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 845270616996 + 21238690225 = 919386^2 + 145735^2 .

It is a cyclic number.

It is not a de Polignac number, because 866509307221 - 2⁷ = 866509307093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (866509307281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 433254653610 + 433254653611.

It is an arithmetic number, because the mean of its divisors is an integer number (433254653611).

Almost surely, 2^866509307221 is an apocalyptic number.

It is an amenable number.

866509307221 is a deficient number, since it is larger than the sum of its proper divisors (1).

866509307221 is an equidigital number, since it uses as much as digits as its factorization.

866509307221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1088640, while the sum is 49.

The spelling of 866509307221 in words is "eight hundred sixty-six billion, five hundred nine million, three hundred seven thousand, two hundred twenty-one".