66211609 has 2 divisors, whose sum is σ = 66211610. Its totient is φ = 66211608.

The previous prime is 66211591. The next prime is 66211619. The reversal of 66211609 is 90611266.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64641600 + 1570009 = 8040^2 + 1253^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66211609 is a prime.

It is not a weakly prime, because it can be changed into another prime (66211619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33105804 + 33105805.

It is an arithmetic number, because the mean of its divisors is an integer number (33105805).

Almost surely, 2^66211609 is an apocalyptic number.

It is an amenable number.

66211609 is a deficient number, since it is larger than the sum of its proper divisors (1).

66211609 is an equidigital number, since it uses as much as digits as its factorization.

66211609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 66211609 is about 8137.0516159110. The cubic root of 66211609 is about 404.5554416803. Note that the first 3 decimals are identical.

The spelling of 66211609 in words is "sixty-six million, two hundred eleven thousand, six hundred nine".