645771 has 24 divisors (see below), whose sum is σ = 1050624. Its totient is φ = 351120.

The previous prime is 645763. The next prime is 645787. The reversal of 645771 is 177546.

It is a happy number.

It is not a de Polignac number, because 645771 - 2³ = 645763 is a prime.

645771 is a lucky number.

It is a congruent number.

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 (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3286 + ... + 3476.

It is an arithmetic number, because the mean of its divisors is an integer number (43776).

2⁶⁴⁵⁷⁷¹ is an apocalyptic number.

645771 is a deficient number, since it is larger than the sum of its proper divisors (404853).

645771 is a wasteful number, since it uses less digits than its factorization.

645771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 231 (or 224 counting only the distinct ones).

The product of its digits is 5880, while the sum is 30.

The square root of 645771 is about 803.5987804869. The cubic root of 645771 is about 86.4356388040.

The spelling of 645771 in words is "six hundred forty-five thousand, seven hundred seventy-one".