19871 has 4 divisors (see below), whose sum is σ = 20544. Its totient is φ = 19200.

The previous prime is 19867. The next prime is 19889. The reversal of 19871 is 17891.

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 19871 - 2² = 19867 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 19871.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19801) 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, 290 + ... + 351.

It is an arithmetic number, because the mean of its divisors is an integer number (5136).

2¹⁹⁸⁷¹ is an apocalyptic number.

19871 is a deficient number, since it is larger than the sum of its proper divisors (673).

19871 is an equidigital number, since it uses as much as digits as its factorization.

19871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 672.

The product of its digits is 504, while the sum is 26.

The square root of 19871 is about 140.9645345468. The cubic root of 19871 is about 27.0856902617.

The spelling of 19871 in words is "nineteen thousand, eight hundred seventy-one".