645810 has 64 divisors (see below), whose sum is σ = 1797120. Its totient is φ = 146880.

The previous prime is 645803. The next prime is 645833. The reversal of 645810 is 18546.

It is a super-2 number, since 2×645810² = 834141112200, which contains 22 as substring.

It is a nialpdrome in base 15.

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 645810.

It is an unprimeable number.

645810 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 31 ways as a sum of consecutive naturals, for example, 6219 + ... + 6321.

It is an arithmetic number, because the mean of its divisors is an integer number (28080).

2⁶⁴⁵⁸¹⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645810, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (898560).

645810 is an abundant number, since it is smaller than the sum of its proper divisors (1151310).

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

645810 is a wasteful number, since it uses less digits than its factorization.

645810 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 143.

The product of its (nonzero) digits is 960, while the sum is 24.

The square root of 645810 is about 803.6230459612. The cubic root of 645810 is about 86.4373788027.

Subtracting from 645810 its reverse (18546), we obtain a square (627264 = 792²).

The spelling of 645810 in words is "six hundred forty-five thousand, eight hundred ten".