645681866 has 8 divisors (see below), whose sum is σ = 968998464. Its totient is φ = 322682380.

The previous prime is 645681863. The next prime is 645681871. The reversal of 645681866 is 668186546.

645681866 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (645681863) 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, 74120 + ... + 82371.

It is an arithmetic number, because the mean of its divisors is an integer number (121124808).

Almost surely, 2^645681866 is an apocalyptic number.

645681866 is a deficient number, since it is larger than the sum of its proper divisors (323316598).

645681866 is a wasteful number, since it uses less digits than its factorization.

645681866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158556.

The product of its digits is 1658880, while the sum is 50.

The square root of 645681866 is about 25410.2708761634. The cubic root of 645681866 is about 864.3166179628.

The spelling of 645681866 in words is "six hundred forty-five million, six hundred eighty-one thousand, eight hundred sixty-six".