665336681 has 2 divisors, whose sum is σ = 665336682. Its totient is φ = 665336680.

The previous prime is 665336629. The next prime is 665336717. The reversal of 665336681 is 186633566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 538008025 + 127328656 = 23195^2 + 11284^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665336681 is a prime.

It is a super-2 number, since 2×665336681² = 885345798168191522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (665336081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332668340 + 332668341.

It is an arithmetic number, because the mean of its divisors is an integer number (332668341).

Almost surely, 2^665336681 is an apocalyptic number.

It is an amenable number.

665336681 is a deficient number, since it is larger than the sum of its proper divisors (1).

665336681 is an equidigital number, since it uses as much as digits as its factorization.

665336681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 466560, while the sum is 44.

The square root of 665336681 is about 25794.1210550001. The cubic root of 665336681 is about 872.9991532484. Note that the first 3 decimals are identical.

It can be divided in two parts, 6653 and 36681, that added together give a palindrome (43334).

The spelling of 665336681 in words is "six hundred sixty-five million, three hundred thirty-six thousand, six hundred eighty-one".