645656 has 48 divisors (see below), whose sum is σ = 1436400. Its totient is φ = 271040.

The previous prime is 645649. The next prime is 645661. The reversal of 645656 is 656546.

Its product of digits (21600) is a multiple of the sum of its prime factors (80).

It is a congruent number.

It is an unprimeable number.

645656 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 22250 + ... + 22278.

It is an arithmetic number, because the mean of its divisors is an integer number (29925).

2⁶⁴⁵⁶⁵⁶ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (718200).

645656 is an abundant number, since it is smaller than the sum of its proper divisors (790744).

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

645656 is a wasteful number, since it uses less digits than its factorization.

645656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80 (or 65 counting only the distinct ones).

The product of its digits is 21600, while the sum is 32.

The square root of 645656 is about 803.5272241810. The cubic root of 645656 is about 86.4305076308.

The spelling of 645656 in words is "six hundred forty-five thousand, six hundred fifty-six".