16391 has 4 divisors (see below), whose sum is σ = 16872. Its totient is φ = 15912.

The previous prime is 16381. The next prime is 16411. The reversal of 16391 is 19361.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19361 = 19 ⋅1019.

It is a cyclic number.

It is not a de Polignac number, because 16391 - 2¹⁴ = 7 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16301) 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, 185 + ... + 258.

It is an arithmetic number, because the mean of its divisors is an integer number (4218).

2¹⁶³⁹¹ is an apocalyptic number.

16391 is a deficient number, since it is larger than the sum of its proper divisors (481).

16391 is an equidigital number, since it uses as much as digits as its factorization.

16391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 480.

The product of its digits is 162, while the sum is 20.

The square root of 16391 is about 128.0273408300. The cubic root of 16391 is about 25.4020334413.

The spelling of 16391 in words is "sixteen thousand, three hundred ninety-one".