818581 has 2 divisors, whose sum is σ = 818582. Its totient is φ = 818580.

The previous prime is 818579. The next prime is 818603. The reversal of 818581 is 185818.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 624100 + 194481 = 790^2 + 441^2 .

It is a cyclic number.

It is not a de Polignac number, because 818581 - 2¹ = 818579 is a prime.

It is a super-2 number, since 2×818581² = 1340149707122, which contains 22 as substring.

Together with 818579, it forms a pair of twin primes.

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

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (818561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 409290 + 409291.

It is an arithmetic number, because the mean of its divisors is an integer number (409291).

2⁸¹⁸⁵⁸¹ is an apocalyptic number.

It is an amenable number.

818581 is a deficient number, since it is larger than the sum of its proper divisors (1).

818581 is an equidigital number, since it uses as much as digits as its factorization.

818581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2560, while the sum is 31.

The square root of 818581 is about 904.7546628783. The cubic root of 818581 is about 93.5449944060.

The spelling of 818581 in words is "eight hundred eighteen thousand, five hundred eighty-one".