816591 has 8 divisors (see below), whose sum is σ = 1093680. Its totient is φ = 541952.

The previous prime is 816589. The next prime is 816593. The reversal of 816591 is 195618.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (816589) and next prime (816593).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 816591 - 2¹ = 816589 is a prime.

It is a super-2 number, since 2×816591² = 1333641722562, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (816593) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 415 + ... + 1343.

It is an arithmetic number, because the mean of its divisors is an integer number (136710).

2⁸¹⁶⁵⁹¹ is an apocalyptic number.

816591 is a deficient number, since it is larger than the sum of its proper divisors (277089).

816591 is a wasteful number, since it uses less digits than its factorization.

816591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1225.

The product of its digits is 2160, while the sum is 30.

The square root of 816591 is about 903.6542480396. The cubic root of 816591 is about 93.4691291414.

It can be divided in two parts, 8165 and 91, that added together give a triangular number (8256 = T₁₂₈).

The spelling of 816591 in words is "eight hundred sixteen thousand, five hundred ninety-one".