645872 has 20 divisors (see below), whose sum is σ = 1286376. Its totient is φ = 313920.

The previous prime is 645857. The next prime is 645877. The reversal of 645872 is 278546.

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 645872.

It is not an unprimeable number, because it can be changed into a prime (645877) by changing a digit.

645872 is an untouchable number, because it is not equal to the sum of proper divisors of any 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 3 ways as a sum of consecutive naturals, for example, 47 + ... + 1137.

2⁶⁴⁵⁸⁷² is an apocalyptic number.

It is an amenable number.

645872 is a deficient number, since it is larger than the sum of its proper divisors (640504).

645872 is a wasteful number, since it uses less digits than its factorization.

645872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1136 (or 1130 counting only the distinct ones).

The product of its digits is 13440, while the sum is 32.

The square root of 645872 is about 803.6616203353. The cubic root of 645872 is about 86.4401448102.

The spelling of 645872 in words is "six hundred forty-five thousand, eight hundred seventy-two".