645864 has 32 divisors (see below), whose sum is σ = 1710720. Its totient is φ = 202496.

The previous prime is 645857. The next prime is 645877. The reversal of 645864 is 468546.

It is a happy number.

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 645864.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 384 + ... + 1199.

It is an arithmetic number, because the mean of its divisors is an integer number (53460).

2⁶⁴⁵⁸⁶⁴ is an apocalyptic number.

It is an amenable number.

645864 is an abundant number, since it is smaller than the sum of its proper divisors (1064856).

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

645864 is a wasteful number, since it uses less digits than its factorization.

645864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1609 (or 1605 counting only the distinct ones).

The product of its digits is 23040, while the sum is 33.

The square root of 645864 is about 803.6566431008. The cubic root of 645864 is about 86.4397879159.

The spelling of 645864 in words is "six hundred forty-five thousand, eight hundred sixty-four".