640555663 has 4 divisors (see below), whose sum is σ = 698788008. Its totient is φ = 582323320.

The previous prime is 640555639. The next prime is 640555667. The reversal of 640555663 is 366555046.

It is a happy number.

640555663 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 640555663 - 2¹⁷ = 640424591 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 (640555667) 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, 29116156 + ... + 29116177.

It is an arithmetic number, because the mean of its divisors is an integer number (174697002).

Almost surely, 2^640555663 is an apocalyptic number.

640555663 is a deficient number, since it is larger than the sum of its proper divisors (58232345).

640555663 is a wasteful number, since it uses less digits than its factorization.

640555663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58232344.

The product of its (nonzero) digits is 324000, while the sum is 40.

The square root of 640555663 is about 25309.2011529404. The cubic root of 640555663 is about 862.0232079604.

The spelling of 640555663 in words is "six hundred forty million, five hundred fifty-five thousand, six hundred sixty-three".