66710221 has 2 divisors, whose sum is σ = 66710222. Its totient is φ = 66710220.

The previous prime is 66710209. The next prime is 66710279. The reversal of 66710221 is 12201766.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 49154121 + 17556100 = 7011^2 + 4190^2 .

It is a cyclic number.

It is not a de Polignac number, because 66710221 - 2²¹ = 64613069 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66710291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33355110 + 33355111.

It is an arithmetic number, because the mean of its divisors is an integer number (33355111).

Almost surely, 2^66710221 is an apocalyptic number.

It is an amenable number.

66710221 is a deficient number, since it is larger than the sum of its proper divisors (1).

66710221 is an equidigital number, since it uses as much as digits as its factorization.

66710221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 66710221 is about 8167.6325211165. The cubic root of 66710221 is about 405.5684158999.

Adding to 66710221 its reverse (12201766), we get a palindrome (78911987).

The spelling of 66710221 in words is "sixty-six million, seven hundred ten thousand, two hundred twenty-one".