66557609 has 2 divisors, whose sum is σ = 66557610. Its totient is φ = 66557608.

The previous prime is 66557597. The next prime is 66557611. The reversal of 66557609 is 90675566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 39100009 + 27457600 = 6253^2 + 5240^2 .

It is a cyclic number.

It is not a de Polignac number, because 66557609 - 2⁸ = 66557353 is a prime.

Together with 66557611, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 66557609.

It is not a weakly prime, because it can be changed into another prime (66557809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33278804 + 33278805.

It is an arithmetic number, because the mean of its divisors is an integer number (33278805).

Almost surely, 2^66557609 is an apocalyptic number.

It is an amenable number.

66557609 is a deficient number, since it is larger than the sum of its proper divisors (1).

66557609 is an equidigital number, since it uses as much as digits as its factorization.

66557609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 340200, while the sum is 44.

The square root of 66557609 is about 8158.2846849077. The cubic root of 66557609 is about 405.2589087774.

The spelling of 66557609 in words is "sixty-six million, five hundred fifty-seven thousand, six hundred nine".