646871 has 4 divisors (see below), whose sum is σ = 664392. Its totient is φ = 629352.

The previous prime is 646859. The next prime is 646873. The reversal of 646871 is 178646.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646871 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646873) 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, 8705 + ... + 8778.

It is an arithmetic number, because the mean of its divisors is an integer number (166098).

2⁶⁴⁶⁸⁷¹ is an apocalyptic number.

646871 is a deficient number, since it is larger than the sum of its proper divisors (17521).

646871 is a wasteful number, since it uses less digits than its factorization.

646871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17520.

The product of its digits is 8064, while the sum is 32.

The square root of 646871 is about 804.2829104239. The cubic root of 646871 is about 86.4846888377.

The spelling of 646871 in words is "six hundred forty-six thousand, eight hundred seventy-one".