645686 has 8 divisors (see below), whose sum is σ = 989280. Its totient is φ = 315928.

The previous prime is 645683. The next prime is 645691. The reversal of 645686 is 686546.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645683) 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 3 ways as a sum of consecutive naturals, for example, 3341 + ... + 3528.

It is an arithmetic number, because the mean of its divisors is an integer number (123660).

2⁶⁴⁵⁶⁸⁶ is an apocalyptic number.

645686 is a deficient number, since it is larger than the sum of its proper divisors (343594).

645686 is a wasteful number, since it uses less digits than its factorization.

645686 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6918.

The product of its digits is 34560, while the sum is 35.

The square root of 645686 is about 803.5458916577. The cubic root of 645686 is about 86.4318462564.

It can be divided in two parts, 645 and 686, that added together give a palindrome (1331).

The spelling of 645686 in words is "six hundred forty-five thousand, six hundred eighty-six".