665718917 has 4 divisors (see below), whose sum is σ = 671826540. Its totient is φ = 659611296.

The previous prime is 665718871. The next prime is 665718931. The reversal of 665718917 is 719817566.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 149793121 + 515925796 = 12239^2 + 22714^2 .

It is a cyclic number.

It is not a de Polignac number, because 665718917 - 2⁸ = 665718661 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 (665718617) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3053648 + ... + 3053865.

It is an arithmetic number, because the mean of its divisors is an integer number (167956635).

Almost surely, 2^665718917 is an apocalyptic number.

It is an amenable number.

665718917 is a deficient number, since it is larger than the sum of its proper divisors (6107623).

665718917 is a wasteful number, since it uses less digits than its factorization.

665718917 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6107622.

The product of its digits is 635040, while the sum is 50.

The square root of 665718917 is about 25801.5293538968. The cubic root of 665718917 is about 873.1663006152.

The spelling of 665718917 in words is "six hundred sixty-five million, seven hundred eighteen thousand, nine hundred seventeen".