645570 has 40 divisors (see below), whose sum is σ = 1738044. Its totient is φ = 171936.

The previous prime is 645529. The next prime is 645571. The reversal of 645570 is 75546.

645570 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 641601 + 3969 = 801^2 + 63^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (645571) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 412 + ... + 1208.

2⁶⁴⁵⁵⁷⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645570, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (869022).

645570 is an abundant number, since it is smaller than the sum of its proper divisors (1092474).

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

645570 is a wasteful number, since it uses less digits than its factorization.

645570 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 816 (or 807 counting only the distinct ones).

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

The square root of 645570 is about 803.4737083440. The cubic root of 645570 is about 86.4266700074.

The spelling of 645570 in words is "six hundred forty-five thousand, five hundred seventy".