816566909 has 2 divisors, whose sum is σ = 816566910. Its totient is φ = 816566908.

The previous prime is 816566869. The next prime is 816566911. The reversal of 816566909 is 909665618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 805310884 + 11256025 = 28378^2 + 3355^2 .

It is a cyclic number.

It is not a de Polignac number, because 816566909 - 2²⁴ = 799789693 is a prime.

Together with 816566911, 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 (816566929) 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, 408283454 + 408283455.

It is an arithmetic number, because the mean of its divisors is an integer number (408283455).

Almost surely, 2^816566909 is an apocalyptic number.

It is an amenable number.

816566909 is a deficient number, since it is larger than the sum of its proper divisors (1).

816566909 is an equidigital number, since it uses as much as digits as its factorization.

816566909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 699840, while the sum is 50.

The square root of 816566909 is about 28575.6348835857. The cubic root of 816566909 is about 934.6820995956.

The spelling of 816566909 in words is "eight hundred sixteen million, five hundred sixty-six thousand, nine hundred nine".