665691569 has 2 divisors, whose sum is σ = 665691570. Its totient is φ = 665691568.

The previous prime is 665691541. The next prime is 665691577. The reversal of 665691569 is 965196566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 380757169 + 284934400 = 19513^2 + 16880^2 .

It is a cyclic number.

It is not a de Polignac number, because 665691569 - 2²⁸ = 397256113 is a prime.

It is a super-3 number, since 3×665691569³ (a number of 27 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 665691569.

It is not a weakly prime, because it can be changed into another prime (665691589) 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, 332845784 + 332845785.

It is an arithmetic number, because the mean of its divisors is an integer number (332845785).

Almost surely, 2^665691569 is an apocalyptic number.

It is an amenable number.

665691569 is a deficient number, since it is larger than the sum of its proper divisors (1).

665691569 is an equidigital number, since it uses as much as digits as its factorization.

665691569 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2624400, while the sum is 53.

The square root of 665691569 is about 25800.9993798690. Note that the first 3 decimals coincide. The cubic root of 665691569 is about 873.1543437775.

The spelling of 665691569 in words is "six hundred sixty-five million, six hundred ninety-one thousand, five hundred sixty-nine".