640844765 has 32 divisors (see below), whose sum is σ = 862327296. Its totient is φ = 453199360.

The previous prime is 640844753. The next prime is 640844777. The reversal of 640844765 is 567448046.

640844765 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (640844753) and next prime (640844777).

It is not a de Polignac number, because 640844765 - 2¹⁴ = 640828381 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 446489 + ... + 447921.

It is an arithmetic number, because the mean of its divisors is an integer number (26947728).

Almost surely, 2^640844765 is an apocalyptic number.

It is an amenable number.

640844765 is a deficient number, since it is larger than the sum of its proper divisors (221482531).

640844765 is a wasteful number, since it uses less digits than its factorization.

640844765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1669.

The product of its (nonzero) digits is 645120, while the sum is 44.

The square root of 640844765 is about 25314.9119097816. The cubic root of 640844765 is about 862.1528741054.

The spelling of 640844765 in words is "six hundred forty million, eight hundred forty-four thousand, seven hundred sixty-five".