668581 has 2 divisors, whose sum is σ = 668582. Its totient is φ = 668580.

The previous prime is 668579. The next prime is 668599. The reversal of 668581 is 185866.

It is a happy number.

668581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 664225 + 4356 = 815^2 + 66^2 .

It is a cyclic number.

It is not a de Polignac number, because 668581 - 2¹ = 668579 is a prime.

It is a super-2 number, since 2×668581² = 894001107122, which contains 22 as substring.

Together with 668579, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334290 + 334291.

It is an arithmetic number, because the mean of its divisors is an integer number (334291).

2⁶⁶⁸⁵⁸¹ is an apocalyptic number.

It is an amenable number.

668581 is a deficient number, since it is larger than the sum of its proper divisors (1).

668581 is an equidigital number, since it uses as much as digits as its factorization.

668581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11520, while the sum is 34.

The square root of 668581 is about 817.6680255458. The cubic root of 668581 is about 87.4415827766.

The spelling of 668581 in words is "six hundred sixty-eight thousand, five hundred eighty-one".