640871 has 24 divisors (see below), whose sum is σ = 861840. Its totient is φ = 470400.

The previous prime is 640859. The next prime is 640873. The reversal of 640871 is 178046.

It is not a de Polignac number, because 640871 - 2¹⁴ = 624487 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 640871.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640873) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15611 + ... + 15651.

It is an arithmetic number, because the mean of its divisors is an integer number (35910).

2⁶⁴⁰⁸⁷¹ is an apocalyptic number.

640871 is a deficient number, since it is larger than the sum of its proper divisors (220969).

640871 is a wasteful number, since it uses less digits than its factorization.

640871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95 (or 88 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 640871 is about 800.5441899108. The cubic root of 640871 is about 86.2164638926.

The spelling of 640871 in words is "six hundred forty thousand, eight hundred seventy-one".