666559 has 2 divisors, whose sum is σ = 666560. Its totient is φ = 666558.

The previous prime is 666557. The next prime is 666599. The reversal of 666559 is 955666.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 666559 - 2¹ = 666557 is a prime.

Together with 666557, 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 (666557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333279 + 333280.

It is an arithmetic number, because the mean of its divisors is an integer number (333280).

2⁶⁶⁶⁵⁵⁹ is an apocalyptic number.

666559 is a deficient number, since it is larger than the sum of its proper divisors (1).

666559 is an equidigital number, since it uses as much as digits as its factorization.

666559 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48600, while the sum is 37.

The square root of 666559 is about 816.4306461666. The cubic root of 666559 is about 87.3533434456.

It can be divided in two parts, 6665 and 59, that added together give a square (6724 = 82²).

The spelling of 666559 in words is "six hundred sixty-six thousand, five hundred fifty-nine".