640780663 has 4 divisors (see below), whose sum is σ = 647125128. Its totient is φ = 634436200.

The previous prime is 640780631. The next prime is 640780691. The reversal of 640780663 is 366087046.

640780663 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 640780663 - 2⁵ = 640780631 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640780603) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3172081 + ... + 3172282.

It is an arithmetic number, because the mean of its divisors is an integer number (161781282).

Almost surely, 2^640780663 is an apocalyptic number.

640780663 is a deficient number, since it is larger than the sum of its proper divisors (6344465).

640780663 is a wasteful number, since it uses less digits than its factorization.

640780663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6344464.

The product of its (nonzero) digits is 145152, while the sum is 40.

The square root of 640780663 is about 25313.6457864133. The cubic root of 640780663 is about 862.1241268594.

The spelling of 640780663 in words is "six hundred forty million, seven hundred eighty thousand, six hundred sixty-three".