645750 has 96 divisors (see below), whose sum is σ = 2044224. Its totient is φ = 144000.

The previous prime is 645739. The next prime is 645751. The reversal of 645750 is 57546.

645750 is nontrivially palindromic in base 4.

It is a Curzon number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645751) by changing a digit.

645750 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 47 ways as a sum of consecutive naturals, for example, 15730 + ... + 15770.

It is an arithmetic number, because the mean of its divisors is an integer number (21294).

2⁶⁴⁵⁷⁵⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645750, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1022112).

645750 is an abundant number, since it is smaller than the sum of its proper divisors (1398474).

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

645750 is a wasteful number, since it uses less digits than its factorization.

645750 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71 (or 58 counting only the distinct ones).

The product of its (nonzero) digits is 4200, while the sum is 27.

The square root of 645750 is about 803.5857141587. The cubic root of 645750 is about 86.4347018526.

The spelling of 645750 in words is "six hundred forty-five thousand, seven hundred fifty".