19939 has 4 divisors (see below), whose sum is σ = 20224. Its totient is φ = 19656.

The previous prime is 19937. The next prime is 19949. The reversal of 19939 is 93991.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 93991 = 193 ⋅487.

It is a cyclic number.

It is not a de Polignac number, because 19939 - 2¹ = 19937 is a prime.

It is a Duffinian number.

19939 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 19939.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19937) 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, 49 + ... + 205.

It is an arithmetic number, because the mean of its divisors is an integer number (5056).

2¹⁹⁹³⁹ is an apocalyptic number.

19939 is a deficient number, since it is larger than the sum of its proper divisors (285).

19939 is a wasteful number, since it uses less digits than its factorization.

19939 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 284.

The product of its digits is 2187, while the sum is 31.

The square root of 19939 is about 141.2055239713. The cubic root of 19939 is about 27.1165514827.

It can be divided in two parts, 1993 and 9, that added together give a palindrome (2002).

The spelling of 19939 in words is "nineteen thousand, nine hundred thirty-nine".