66648221 has 2 divisors, whose sum is σ = 66648222. Its totient is φ = 66648220.

The previous prime is 66648217. The next prime is 66648223. The reversal of 66648221 is 12284666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 35164900 + 31483321 = 5930^2 + 5611^2 .

It is a cyclic number.

It is not a de Polignac number, because 66648221 - 2² = 66648217 is a prime.

Together with 66648223, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66648223) 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, 33324110 + 33324111.

It is an arithmetic number, because the mean of its divisors is an integer number (33324111).

Almost surely, 2^66648221 is an apocalyptic number.

It is an amenable number.

66648221 is a deficient number, since it is larger than the sum of its proper divisors (1).

66648221 is an equidigital number, since it uses as much as digits as its factorization.

66648221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27648, while the sum is 35.

The square root of 66648221 is about 8163.8361693508. The cubic root of 66648221 is about 405.4427328318.

The spelling of 66648221 in words is "sixty-six million, six hundred forty-eight thousand, two hundred twenty-one".