664075681 has 2 divisors, whose sum is σ = 664075682. Its totient is φ = 664075680.

The previous prime is 664075663. The next prime is 664075721. The reversal of 664075681 is 186570466.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 528586081 + 135489600 = 22991^2 + 11640^2 .

It is a cyclic number.

It is not a de Polignac number, because 664075681 - 2⁹ = 664075169 is a prime.

It is a super-2 number, since 2×664075681² = 881993020191227522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (664075661) 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, 332037840 + 332037841.

It is an arithmetic number, because the mean of its divisors is an integer number (332037841).

Almost surely, 2^664075681 is an apocalyptic number.

It is an amenable number.

664075681 is a deficient number, since it is larger than the sum of its proper divisors (1).

664075681 is an equidigital number, since it uses as much as digits as its factorization.

664075681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 241920, while the sum is 43.

The square root of 664075681 is about 25769.6659078072. The cubic root of 664075681 is about 872.4472781995.

The spelling of 664075681 in words is "six hundred sixty-four million, seventy-five thousand, six hundred eighty-one".