645428 has 36 divisors (see below), whose sum is σ = 1364580. Its totient is φ = 266112.

The previous prime is 645419. The next prime is 645431. The reversal of 645428 is 824546.

645428 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 362404 + 283024 = 602^2 + 532^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 645428.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645428.

It is an unprimeable number.

645428 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, 7208 + ... + 7296.

It is an arithmetic number, because the mean of its divisors is an integer number (37905).

2⁶⁴⁵⁴²⁸ 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 645428, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (682290).

645428 is an abundant number, since it is smaller than the sum of its proper divisors (719152).

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

645428 is a wasteful number, since it uses less digits than its factorization.

645428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144 (or 135 counting only the distinct ones).

The product of its digits is 7680, while the sum is 29.

The square root of 645428 is about 803.3853371826. The cubic root of 645428 is about 86.4203327204.

The spelling of 645428 in words is "six hundred forty-five thousand, four hundred twenty-eight".