665886491 has 2 divisors, whose sum is σ = 665886492. Its totient is φ = 665886490.

The previous prime is 665886467. The next prime is 665886499. The reversal of 665886491 is 194688566.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665886491 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (665886499) 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, 332943245 + 332943246.

It is an arithmetic number, because the mean of its divisors is an integer number (332943246).

Almost surely, 2^665886491 is an apocalyptic number.

665886491 is a deficient number, since it is larger than the sum of its proper divisors (1).

665886491 is an equidigital number, since it uses as much as digits as its factorization.

665886491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2488320, while the sum is 53.

The square root of 665886491 is about 25804.7765152113. The cubic root of 665886491 is about 873.2395586076.

The spelling of 665886491 in words is "six hundred sixty-five million, eight hundred eighty-six thousand, four hundred ninety-one".