666765 has 32 divisors (see below), whose sum is σ = 1296000. Its totient is φ = 322560.

The previous prime is 666751. The next prime is 666769. The reversal of 666765 is 567666.

It is not a de Polignac number, because 666765 - 2⁴ = 666749 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666769) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1261 + ... + 1709.

It is an arithmetic number, because the mean of its divisors is an integer number (40500).

2⁶⁶⁶⁷⁶⁵ is an apocalyptic number.

It is an amenable number.

666765 is a deficient number, since it is larger than the sum of its proper divisors (629235).

666765 is a wasteful number, since it uses less digits than its factorization.

666765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 474 (or 468 counting only the distinct ones).

The product of its digits is 45360, while the sum is 36.

The square root of 666765 is about 816.5567953302. The cubic root of 666765 is about 87.3623413664.

Subtracting from 666765 its reverse (567666), we obtain a palindrome (99099).

It can be divided in two parts, 666 and 765, that added together give a triangular number (1431 = T₅₃).

The spelling of 666765 in words is "six hundred sixty-six thousand, seven hundred sixty-five".