816391 has 4 divisors (see below), whose sum is σ = 864432. Its totient is φ = 768352.

The previous prime is 816377. The next prime is 816401. The reversal of 816391 is 193618.

It is a happy number.

816391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 816391 - 2¹⁷ = 685319 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (816341) 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, 23995 + ... + 24028.

It is an arithmetic number, because the mean of its divisors is an integer number (216108).

2⁸¹⁶³⁹¹ is an apocalyptic number.

816391 is a deficient number, since it is larger than the sum of its proper divisors (48041).

816391 is a wasteful number, since it uses less digits than its factorization.

816391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48040.

The product of its digits is 1296, while the sum is 28.

The square root of 816391 is about 903.5435794692. The cubic root of 816391 is about 93.4614976784.

The spelling of 816391 in words is "eight hundred sixteen thousand, three hundred ninety-one".