19381 has 2 divisors, whose sum is σ = 19382. Its totient is φ = 19380.

The previous prime is 19379. The next prime is 19387. The reversal of 19381 is 18391.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18225 + 1156 = 135^2 + 34^2 .

It is a cyclic number.

It is not a de Polignac number, because 19381 - 2¹ = 19379 is a prime.

It is a super-2 number, since 2×19381² = 751246322, which contains 22 as substring.

Together with 19379, it forms a pair of twin primes.

It is a zygodrome in base 5.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9690 + 9691.

It is an arithmetic number, because the mean of its divisors is an integer number (9691).

2¹⁹³⁸¹ is an apocalyptic number.

It is an amenable number.

19381 is a deficient number, since it is larger than the sum of its proper divisors (1).

19381 is an equidigital number, since it uses as much as digits as its factorization.

19381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 216, while the sum is 22.

The square root of 19381 is about 139.2156600387. The cubic root of 19381 is about 26.8611989713.

Subtracting from 19381 its reverse (18391), we obtain a triangular number (990 = T₄₄).

It can be divided in two parts, 19 and 381, that added together give a square (400 = 20²).

The spelling of 19381 in words is "nineteen thousand, three hundred eighty-one".