666815797 has 6 divisors (see below), whose sum is σ = 689020854. Its totient is φ = 645304680.

The previous prime is 666815789. The next prime is 666815819. The reversal of 666815797 is 797518666.

It can be written as a sum of positive squares in only one way, i.e., 485805681 + 181010116 = 22041^2 + 13454^2 .

It is not a de Polignac number, because 666815797 - 2³ = 666815789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666815707) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 345978 + ... + 347899.

It is an arithmetic number, because the mean of its divisors is an integer number (114836809).

Almost surely, 2^666815797 is an apocalyptic number.

It is an amenable number.

666815797 is a deficient number, since it is larger than the sum of its proper divisors (22205057).

666815797 is an equidigital number, since it uses as much as digits as its factorization.

666815797 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 693939 (or 693908 counting only the distinct ones).

The product of its digits is 3810240, while the sum is 55.

The square root of 666815797 is about 25822.7767097189. The cubic root of 666815797 is about 873.6455985528.

The spelling of 666815797 in words is "six hundred sixty-six million, eight hundred fifteen thousand, seven hundred ninety-seven".