645678 has 32 divisors (see below), whose sum is σ = 1566720. Its totient is φ = 195480.

The previous prime is 645661. The next prime is 645683. The reversal of 645678 is 876546.

It is a happy number.

645678 is a `hidden beast` number, since 645 + 6 + 7 + 8 = 666.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

645678 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 15 ways as a sum of consecutive naturals, for example, 51 + ... + 1137.

It is an arithmetic number, because the mean of its divisors is an integer number (48960).

2⁶⁴⁵⁶⁷⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645678, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (783360).

645678 is an abundant number, since it is smaller than the sum of its proper divisors (921042).

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

645678 is a wasteful number, since it uses less digits than its factorization.

645678 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1109 (or 1103 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 645678 is about 803.5409137063. The cubic root of 645678 is about 86.4314892936.

The spelling of 645678 in words is "six hundred forty-five thousand, six hundred seventy-eight".