665871 has 4 divisors (see below), whose sum is σ = 887832. Its totient is φ = 443912.

The previous prime is 665857. The next prime is 665897. The reversal of 665871 is 178566.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 665871 - 2⁹ = 665359 is a prime.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665801) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110976 + ... + 110981.

It is an arithmetic number, because the mean of its divisors is an integer number (221958).

2⁶⁶⁵⁸⁷¹ is an apocalyptic number.

665871 is a deficient number, since it is larger than the sum of its proper divisors (221961).

665871 is a wasteful number, since it uses less digits than its factorization.

665871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221960.

The product of its digits is 10080, while the sum is 33.

The square root of 665871 is about 816.0091911247. The cubic root of 665871 is about 87.3232786954.

The spelling of 665871 in words is "six hundred sixty-five thousand, eight hundred seventy-one".