645256 has 8 divisors (see below), whose sum is σ = 1209870. Its totient is φ = 322624.

The previous prime is 645233. The next prime is 645257. The reversal of 645256 is 652546.

It can be written as a sum of positive squares in only one way, i.e., 324900 + 320356 = 570^2 + 566^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (645257) by changing a digit.

645256 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 as a sum of consecutive naturals, namely, 40321 + ... + 40336.

2⁶⁴⁵²⁵⁶ is an apocalyptic number.

It is an amenable number.

645256 is a deficient number, since it is larger than the sum of its proper divisors (564614).

645256 is a wasteful number, since it uses less digits than its factorization.

645256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80663 (or 80659 counting only the distinct ones).

The product of its digits is 7200, while the sum is 28.

The square root of 645256 is about 803.2782830377. The cubic root of 645256 is about 86.4126553250.

The spelling of 645256 in words is "six hundred forty-five thousand, two hundred fifty-six".