645870 has 16 divisors (see below), whose sum is σ = 1550160. Its totient is φ = 172224.

The previous prime is 645857. The next prime is 645877. The reversal of 645870 is 78546.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30), and also a Moran number because the ratio is a prime number: 21529 = 645870 / (6 + 4 + 5 + 8 + 7 + 0).

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 645870.

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

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10735 + ... + 10794.

It is an arithmetic number, because the mean of its divisors is an integer number (96885).

2⁶⁴⁵⁸⁷⁰ is an apocalyptic number.

645870 is an abundant number, since it is smaller than the sum of its proper divisors (904290).

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

645870 is a wasteful number, since it uses less digits than its factorization.

645870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21539.

The product of its (nonzero) digits is 6720, while the sum is 30.

The square root of 645870 is about 803.6603760296. The cubic root of 645870 is about 86.4400555869.

The spelling of 645870 in words is "six hundred forty-five thousand, eight hundred seventy".