20871 has 8 divisors (see below), whose sum is σ = 30960. Its totient is φ = 13896.

The previous prime is 20857. The next prime is 20873. The reversal of 20871 is 17802.

It is not a de Polignac number, because 20871 - 2⁶ = 20807 is a prime.

It is a nialpdrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20873) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 360 + ... + 413.

It is an arithmetic number, because the mean of its divisors is an integer number (3870).

2²⁰⁸⁷¹ is an apocalyptic number.

20871 is a deficient number, since it is larger than the sum of its proper divisors (10089).

20871 is an equidigital number, since it uses as much as digits as its factorization.

20871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 782 (or 776 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 20871 is about 144.4679895340. The cubic root of 20871 is about 27.5326334359.

The spelling of 20871 in words is "twenty thousand, eight hundred seventy-one".