664678681 has 2 divisors, whose sum is σ = 664678682. Its totient is φ = 664678680.

The previous prime is 664678643. The next prime is 664678709. The reversal of 664678681 is 186876466.

It is a happy number.

664678681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 645973056 + 18705625 = 25416^2 + 4325^2 .

It is a cyclic number.

It is not a de Polignac number, because 664678681 - 2⁹ = 664678169 is a prime.

It is a super-2 number, since 2×664678681² = 883595497951799522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (664678381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332339340 + 332339341.

It is an arithmetic number, because the mean of its divisors is an integer number (332339341).

Almost surely, 2^664678681 is an apocalyptic number.

It is an amenable number.

664678681 is a deficient number, since it is larger than the sum of its proper divisors (1).

664678681 is an equidigital number, since it uses as much as digits as its factorization.

664678681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2322432, while the sum is 52.

The square root of 664678681 is about 25781.3630555097. The cubic root of 664678681 is about 872.7112674658.

The spelling of 664678681 in words is "six hundred sixty-four million, six hundred seventy-eight thousand, six hundred eighty-one".