666640769 has 2 divisors, whose sum is σ = 666640770. Its totient is φ = 666640768.

The previous prime is 666640753. The next prime is 666640813. The reversal of 666640769 is 967046666.

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., 338560000 + 328080769 = 18400^2 + 18113^2 .

It is a cyclic number.

It is not a de Polignac number, because 666640769 - 2⁴ = 666640753 is a prime.

It is a super-2 number, since 2×666640769² = 888819829785822722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (666640069) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333320384 + 333320385.

It is an arithmetic number, because the mean of its divisors is an integer number (333320385).

Almost surely, 2^666640769 is an apocalyptic number.

It is an amenable number.

666640769 is a deficient number, since it is larger than the sum of its proper divisors (1).

666640769 is an equidigital number, since it uses as much as digits as its factorization.

666640769 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1959552, while the sum is 50.

The square root of 666640769 is about 25819.3874636871. The cubic root of 666640769 is about 873.5691527420.

The spelling of 666640769 in words is "six hundred sixty-six million, six hundred forty thousand, seven hundred sixty-nine".