645760 has 32 divisors (see below), whose sum is σ = 1545300. Its totient is φ = 258048.

The previous prime is 645751. The next prime is 645763. The reversal of 645760 is 67546.

It can be written as a sum of positive squares in 2 ways, for example, as 627264 + 18496 = 792^2 + 136^2 .

It is a tau number, because it is divible by the number of its divisors (32).

It is not an unprimeable number, because it can be changed into a prime (645763) by changing a digit.

645760 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 3 ways as a sum of consecutive naturals, for example, 136 + ... + 1144.

2⁶⁴⁵⁷⁶⁰ 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 645760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (772650).

645760 is an abundant number, since it is smaller than the sum of its proper divisors (899540).

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

645760 is a wasteful number, since it uses less digits than its factorization.

645760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1028 (or 1016 counting only the distinct ones).

The product of its (nonzero) digits is 5040, while the sum is 28.

The square root of 645760 is about 803.5919362463. The cubic root of 645760 is about 86.4351480225.

The spelling of 645760 in words is "six hundred forty-five thousand, seven hundred sixty".