645866660 has 12 divisors (see below), whose sum is σ = 1356320028. Its totient is φ = 258346656.

The previous prime is 645866653. The next prime is 645866671. The reversal of 645866660 is 66668546.

645866660 is digitally balanced in base 2 and base 6, because in such bases it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 358496356 + 287370304 = 18934^2 + 16952^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16146647 + ... + 16146686.

It is an arithmetic number, because the mean of its divisors is an integer number (113026669).

Almost surely, 2^645866660 is an apocalyptic number.

It is an amenable number.

645866660 is an abundant number, since it is smaller than the sum of its proper divisors (710453368).

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

645866660 is a wasteful number, since it uses less digits than its factorization.

645866660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32293342 (or 32293340 counting only the distinct ones).

The product of its (nonzero) digits is 1244160, while the sum is 47.

The square root of 645866660 is about 25413.9068228401. The cubic root of 645866660 is about 864.3990658361.

The spelling of 645866660 in words is "six hundred forty-five million, eight hundred sixty-six thousand, six hundred sixty".