645804 has 18 divisors (see below), whose sum is σ = 1632540. Its totient is φ = 215256.

The previous prime is 645803. The next prime is 645833. The reversal of 645804 is 408546.

It is a tau number, because it is divible by the number of its divisors (18).

It is not an unprimeable number, because it can be changed into a prime (645803) by changing a digit.

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 5 ways as a sum of consecutive naturals, for example, 8934 + ... + 9005.

2⁶⁴⁵⁸⁰⁴ is an apocalyptic number.

It is an amenable number.

645804 is an abundant number, since it is smaller than the sum of its proper divisors (986736).

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

645804 is a wasteful number, since it uses less digits than its factorization.

645804 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17949 (or 17944 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 645804 is about 803.6193128590. The cubic root of 645804 is about 86.4371111151.

The spelling of 645804 in words is "six hundred forty-five thousand, eight hundred four".