66618221 has 2 divisors, whose sum is σ = 66618222. Its totient is φ = 66618220.

The previous prime is 66618203. The next prime is 66618239. The reversal of 66618221 is 12281666.

It is a balanced prime because it is at equal distance from previous prime (66618203) and next prime (66618239).

It can be written as a sum of positive squares in only one way, i.e., 37576900 + 29041321 = 6130^2 + 5389^2 .

It is a cyclic number.

It is not a de Polignac number, because 66618221 - 2¹⁰ = 66617197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66618421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33309110 + 33309111.

It is an arithmetic number, because the mean of its divisors is an integer number (33309111).

Almost surely, 2^66618221 is an apocalyptic number.

It is an amenable number.

66618221 is a deficient number, since it is larger than the sum of its proper divisors (1).

66618221 is an equidigital number, since it uses as much as digits as its factorization.

66618221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6912, while the sum is 32.

The square root of 66618221 is about 8161.9985910315. The cubic root of 66618221 is about 405.3818904604.

Adding to 66618221 its reverse (12281666), we get a palindrome (78899887).

The spelling of 66618221 in words is "sixty-six million, six hundred eighteen thousand, two hundred twenty-one".