866161661 has 2 divisors, whose sum is σ = 866161662. Its totient is φ = 866161660.

The previous prime is 866161657. The next prime is 866161663. The reversal of 866161661 is 166161668.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 564062500 + 302099161 = 23750^2 + 17381^2 .

It is a cyclic number.

It is not a de Polignac number, because 866161661 - 2² = 866161657 is a prime.

Together with 866161663, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (866161663) 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, 433080830 + 433080831.

It is an arithmetic number, because the mean of its divisors is an integer number (433080831).

Almost surely, 2^866161661 is an apocalyptic number.

It is an amenable number.

866161661 is a deficient number, since it is larger than the sum of its proper divisors (1).

866161661 is an equidigital number, since it uses as much as digits as its factorization.

866161661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 62208, while the sum is 41.

The square root of 866161661 is about 29430.6245431523. The cubic root of 866161661 is about 953.2342805324.

The spelling of 866161661 in words is "eight hundred sixty-six million, one hundred sixty-one thousand, six hundred sixty-one".