640735687 has 2 divisors, whose sum is σ = 640735688. Its totient is φ = 640735686.

The previous prime is 640735609. The next prime is 640735703. The reversal of 640735687 is 786537046.

640735687 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 is a cyclic number.

It is not a de Polignac number, because 640735687 - 2¹⁹ = 640211399 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640736687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320367843 + 320367844.

It is an arithmetic number, because the mean of its divisors is an integer number (320367844).

Almost surely, 2^640735687 is an apocalyptic number.

640735687 is a deficient number, since it is larger than the sum of its proper divisors (1).

640735687 is an equidigital number, since it uses as much as digits as its factorization.

640735687 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 846720, while the sum is 46.

The square root of 640735687 is about 25312.7573962222. The cubic root of 640735687 is about 862.1039557337.

The spelling of 640735687 in words is "six hundred forty million, seven hundred thirty-five thousand, six hundred eighty-seven".