640908763 has 4 divisors (see below), whose sum is σ = 699173208. Its totient is φ = 582644320.

The previous prime is 640908733. The next prime is 640908769. The reversal of 640908763 is 367809046.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 640908763 - 2⁹ = 640908251 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640908769) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29132206 + ... + 29132227.

It is an arithmetic number, because the mean of its divisors is an integer number (174793302).

Almost surely, 2^640908763 is an apocalyptic number.

640908763 is a deficient number, since it is larger than the sum of its proper divisors (58264445).

640908763 is a wasteful number, since it uses less digits than its factorization.

640908763 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58264444.

The product of its (nonzero) digits is 217728, while the sum is 43.

The square root of 640908763 is about 25316.1759158053. The cubic root of 640908763 is about 862.1815727992.

The spelling of 640908763 in words is "six hundred forty million, nine hundred eight thousand, seven hundred sixty-three".