816581 has 2 divisors, whose sum is σ = 816582. Its totient is φ = 816580.

The previous prime is 816559. The next prime is 816587. The reversal of 816581 is 185618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 504100 + 312481 = 710^2 + 559^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-816581 is a prime.

It is a super-2 number, since 2×816581² = 1333609059122, which contains 22 as substring.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a plaindrome in base 13.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 816581.

It is not a weakly prime, because it can be changed into another prime (816587) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 408290 + 408291.

It is an arithmetic number, because the mean of its divisors is an integer number (408291).

2⁸¹⁶⁵⁸¹ is an apocalyptic number.

It is an amenable number.

816581 is a deficient number, since it is larger than the sum of its proper divisors (1).

816581 is an equidigital number, since it uses as much as digits as its factorization.

816581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1920, while the sum is 29.

The square root of 816581 is about 903.6487149330. The cubic root of 816581 is about 93.4687475979.

The spelling of 816581 in words is "eight hundred sixteen thousand, five hundred eighty-one".