640665911 has 2 divisors, whose sum is σ = 640665912. Its totient is φ = 640665910.

The previous prime is 640665899. The next prime is 640665917. The reversal of 640665911 is 119566046.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640665911 - 2²² = 636471607 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640665917) 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, 320332955 + 320332956.

It is an arithmetic number, because the mean of its divisors is an integer number (320332956).

Almost surely, 2^640665911 is an apocalyptic number.

640665911 is a deficient number, since it is larger than the sum of its proper divisors (1).

640665911 is an equidigital number, since it uses as much as digits as its factorization.

640665911 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 38880, while the sum is 38.

The square root of 640665911 is about 25311.3790813539. The cubic root of 640665911 is about 862.0726602762.

The spelling of 640665911 in words is "six hundred forty million, six hundred sixty-five thousand, nine hundred eleven".