640765693 has 2 divisors, whose sum is σ = 640765694. Its totient is φ = 640765692.

The previous prime is 640765687. The next prime is 640765721. The reversal of 640765693 is 396567046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 358458489 + 282307204 = 18933^2 + 16802^2 .

It is a cyclic number.

It is not a de Polignac number, because 640765693 - 2²⁵ = 607211261 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640765613) 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, 320382846 + 320382847.

It is an arithmetic number, because the mean of its divisors is an integer number (320382847).

Almost surely, 2^640765693 is an apocalyptic number.

It is an amenable number.

640765693 is a deficient number, since it is larger than the sum of its proper divisors (1).

640765693 is an equidigital number, since it uses as much as digits as its factorization.

640765693 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 816480, while the sum is 46.

The square root of 640765693 is about 25313.3500943672. The cubic root of 640765693 is about 862.1174131223.

The spelling of 640765693 in words is "six hundred forty million, seven hundred sixty-five thousand, six hundred ninety-three".