645755 has 16 divisors (see below), whose sum is σ = 864000. Its totient is φ = 459360.

The previous prime is 645751. The next prime is 645763. The reversal of 645755 is 557546.

It is a happy number.

It is not a de Polignac number, because 645755 - 2² = 645751 is a prime.

It is not an unprimeable number, because it can be changed into a prime (645751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3146 + ... + 3344.

It is an arithmetic number, because the mean of its divisors is an integer number (54000).

2⁶⁴⁵⁷⁵⁵ is an apocalyptic number.

645755 is a deficient number, since it is larger than the sum of its proper divisors (218245).

645755 is a wasteful number, since it uses less digits than its factorization.

645755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 274.

The product of its digits is 21000, while the sum is 32.

The square root of 645755 is about 803.5888252085. The cubic root of 645755 is about 86.4349249381.

Subtracting from 645755 its reverse (557546), we obtain a square (88209 = 297²).

The spelling of 645755 in words is "six hundred forty-five thousand, seven hundred fifty-five".