645768 has 24 divisors (see below), whose sum is σ = 1749150. Its totient is φ = 215232.

The previous prime is 645763. The next prime is 645787. The reversal of 645768 is 867546.

It is a happy number.

645768 is a `hidden beast` number, since 645 + 7 + 6 + 8 = 666.

It can be written as a sum of positive squares in only one way, i.e., 544644 + 101124 = 738^2 + 318^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (645763) by changing a digit.

645768 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 5 ways as a sum of consecutive naturals, for example, 4413 + ... + 4556.

2⁶⁴⁵⁷⁶⁸ is an apocalyptic number.

It is an amenable number.

645768 is an abundant number, since it is smaller than the sum of its proper divisors (1103382).

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

645768 is a wasteful number, since it uses less digits than its factorization.

645768 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8981 (or 8974 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 645768 is about 803.5969138816. The cubic root of 645768 is about 86.4355049550.

It can be divided in two parts, 64 and 5768, that added together give a cube (5832 = 18³).

The spelling of 645768 in words is "six hundred forty-five thousand, seven hundred sixty-eight".