640647 has 12 divisors (see below), whose sum is σ = 1057680. Its totient is φ = 366048.

The previous prime is 640631. The next prime is 640649. The reversal of 640647 is 746046.

640647 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 640647 - 2⁴ = 640631 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

640647 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 640647.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640647.

It is not an unprimeable number, because it can be changed into a prime (640649) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5022 + ... + 5147.

It is an arithmetic number, because the mean of its divisors is an integer number (88140).

2⁶⁴⁰⁶⁴⁷ is an apocalyptic number.

640647 is a deficient number, since it is larger than the sum of its proper divisors (417033).

640647 is a wasteful number, since it uses less digits than its factorization.

640647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10182 (or 10179 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 27.

The square root of 640647 is about 800.4042728522. The cubic root of 640647 is about 86.2064178052.

The spelling of 640647 in words is "six hundred forty thousand, six hundred forty-seven".