19931 has 4 divisors (see below), whose sum is σ = 21000. Its totient is φ = 18864.

The previous prime is 19927. The next prime is 19937. The reversal of 19931 is 13991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13991 = 17 ⋅823.

It is a cyclic number.

It is not a de Polignac number, because 19931 - 2² = 19927 is a prime.

It is a super-2 number, since 2×19931² = 794489522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 19897 and 19906.

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, 506 + ... + 543.

It is an arithmetic number, because the mean of its divisors is an integer number (5250).

2¹⁹⁹³¹ is an apocalyptic number.

19931 is a deficient number, since it is larger than the sum of its proper divisors (1069).

19931 is a wasteful number, since it uses less digits than its factorization.

19931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1068.

The product of its digits is 243, while the sum is 23.

The square root of 19931 is about 141.1771936256. The cubic root of 19931 is about 27.1129243962.

It can be divided in two parts, 19 and 931, that multiplied together give a square (17689 = 133²).

The spelling of 19931 in words is "nineteen thousand, nine hundred thirty-one".