665717491 has 2 divisors, whose sum is σ = 665717492. Its totient is φ = 665717490.

The previous prime is 665717489. The next prime is 665717539. The reversal of 665717491 is 194717566.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 665717491 - 2¹ = 665717489 is a prime.

Together with 665717489, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (665717401) 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, 332858745 + 332858746.

It is an arithmetic number, because the mean of its divisors is an integer number (332858746).

Almost surely, 2^665717491 is an apocalyptic number.

665717491 is a deficient number, since it is larger than the sum of its proper divisors (1).

665717491 is an equidigital number, since it uses as much as digits as its factorization.

665717491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 317520, while the sum is 46.

The square root of 665717491 is about 25801.5017198612. The cubic root of 665717491 is about 873.1656771608.

The spelling of 665717491 in words is "six hundred sixty-five million, seven hundred seventeen thousand, four hundred ninety-one".