66444221 has 2 divisors, whose sum is σ = 66444222. Its totient is φ = 66444220.

The previous prime is 66444199. The next prime is 66444223. The reversal of 66444221 is 12244466.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 54096025 + 12348196 = 7355^2 + 3514^2 .

It is a cyclic number.

It is not a de Polignac number, because 66444221 - 2¹⁰ = 66443197 is a prime.

It is a Sophie Germain prime.

Together with 66444223, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66444223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33222110 + 33222111.

It is an arithmetic number, because the mean of its divisors is an integer number (33222111).

Almost surely, 2^66444221 is an apocalyptic number.

It is an amenable number.

66444221 is a deficient number, since it is larger than the sum of its proper divisors (1).

66444221 is an equidigital number, since it uses as much as digits as its factorization.

66444221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9216, while the sum is 29.

The square root of 66444221 is about 8151.3324677626. The cubic root of 66444221 is about 405.0286440138.

Adding to 66444221 its reverse (12244466), we get a palindrome (78688687).

The spelling of 66444221 in words is "sixty-six million, four hundred forty-four thousand, two hundred twenty-one".