645680 has 40 divisors (see below), whose sum is σ = 1717152. Its totient is φ = 221184.

The previous prime is 645661. The next prime is 645683. The reversal of 645680 is 86546.

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (645683) by changing a digit.

645680 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 7 ways as a sum of consecutive naturals, for example, 17 + ... + 1136.

2⁶⁴⁵⁶⁸⁰ 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 645680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (858576).

645680 is an abundant number, since it is smaller than the sum of its proper divisors (1071472).

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

645680 is a wasteful number, since it uses less digits than its factorization.

645680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1173 (or 1167 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 645680 is about 803.5421581971. The cubic root of 645680 is about 86.4315785346.

The spelling of 645680 in words is "six hundred forty-five thousand, six hundred eighty".