645657 has 8 divisors (see below), whose sum is σ = 871584. Its totient is φ = 425088.

The previous prime is 645649. The next prime is 645661. The reversal of 645657 is 756546.

645657 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 645657 - 2³ = 645649 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645657.

It is not an unprimeable number, because it can be changed into a prime (645647) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1048 + ... + 1545.

It is an arithmetic number, because the mean of its divisors is an integer number (108948).

2⁶⁴⁵⁶⁵⁷ is an apocalyptic number.

It is an amenable number.

645657 is a deficient number, since it is larger than the sum of its proper divisors (225927).

645657 is a wasteful number, since it uses less digits than its factorization.

645657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2679.

The product of its digits is 25200, while the sum is 33.

The square root of 645657 is about 803.5278464372. The cubic root of 645657 is about 86.4305522523.

Subtracting 645657 from its reverse (756546), we obtain a square (110889 = 333²).

The spelling of 645657 in words is "six hundred forty-five thousand, six hundred fifty-seven".