645640640 has 28 divisors (see below), whose sum is σ = 1537432536. Its totient is φ = 258256128.

The previous prime is 645640607. The next prime is 645640643. The reversal of 645640640 is 46046546.

645640640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 645640640.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645640643) 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, 1008494 + ... + 1009133.

Almost surely, 2^645640640 is an apocalyptic number.

It is an amenable number.

645640640 is an abundant number, since it is smaller than the sum of its proper divisors (891791896).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

645640640 is a wasteful number, since it uses less digits than its factorization.

645640640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2017644 (or 2017634 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 35.

The square root of 645640640 is about 25409.4596558054. The cubic root of 645640640 is about 864.2982223838.

The spelling of 645640640 in words is "six hundred forty-five million, six hundred forty thousand, six hundred forty".