665814491 has 2 divisors, whose sum is σ = 665814492. Its totient is φ = 665814490.

The previous prime is 665814481. The next prime is 665814517. The reversal of 665814491 is 194418566.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 665814491 - 2⁶ = 665814427 is a prime.

It is not a weakly prime, because it can be changed into another prime (665814431) 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 as a sum of consecutive naturals, namely, 332907245 + 332907246.

It is an arithmetic number, because the mean of its divisors is an integer number (332907246).

Almost surely, 2^665814491 is an apocalyptic number.

665814491 is a deficient number, since it is larger than the sum of its proper divisors (1).

665814491 is an equidigital number, since it uses as much as digits as its factorization.

665814491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 207360, while the sum is 44.

The square root of 665814491 is about 25803.3813869423. The cubic root of 665814491 is about 873.2080840168.

The spelling of 665814491 in words is "six hundred sixty-five million, eight hundred fourteen thousand, four hundred ninety-one".