918581 has 2 divisors, whose sum is σ = 918582. Its totient is φ = 918580.

The previous prime is 918563. The next prime is 918583. The reversal of 918581 is 185819.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 872356 + 46225 = 934^2 + 215^2 .

It is an emirp because it is prime and its reverse (185819) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 918581 - 2¹⁰ = 917557 is a prime.

It is a super-2 number, since 2×918581² = 1687582107122, which contains 22 as substring.

Together with 918583, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (918583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 459290 + 459291.

It is an arithmetic number, because the mean of its divisors is an integer number (459291).

2⁹¹⁸⁵⁸¹ is an apocalyptic number.

It is an amenable number.

918581 is a deficient number, since it is larger than the sum of its proper divisors (1).

918581 is an equidigital number, since it uses as much as digits as its factorization.

918581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2880, while the sum is 32.

The square root of 918581 is about 958.4263143299. The cubic root of 918581 is about 97.2088531398.

The spelling of 918581 in words is "nine hundred eighteen thousand, five hundred eighty-one".