666091 has 2 divisors, whose sum is σ = 666092. Its totient is φ = 666090.

The previous prime is 666089. The next prime is 666109. The reversal of 666091 is 190666.

It is a happy number.

Together with next prime (666109) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 666091 - 2¹ = 666089 is a prime.

Together with 666089, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (666031) 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, 333045 + 333046.

It is an arithmetic number, because the mean of its divisors is an integer number (333046).

2⁶⁶⁶⁰⁹¹ is an apocalyptic number.

666091 is a deficient number, since it is larger than the sum of its proper divisors (1).

666091 is an equidigital number, since it uses as much as digits as its factorization.

666091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 666091 is about 816.1439823953. The cubic root of 666091 is about 87.3328946750.

The spelling of 666091 in words is "six hundred sixty-six thousand, ninety-one".