666224021 has 2 divisors, whose sum is σ = 666224022. Its totient is φ = 666224020.

The previous prime is 666224017. The next prime is 666224059. The reversal of 666224021 is 120422666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 648466225 + 17757796 = 25465^2 + 4214^2 .

It is a cyclic number.

It is not a de Polignac number, because 666224021 - 2² = 666224017 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666224011) 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, 333112010 + 333112011.

It is an arithmetic number, because the mean of its divisors is an integer number (333112011).

Almost surely, 2^666224021 is an apocalyptic number.

It is an amenable number.

666224021 is a deficient number, since it is larger than the sum of its proper divisors (1).

666224021 is an equidigital number, since it uses as much as digits as its factorization.

666224021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6912, while the sum is 29.

The square root of 666224021 is about 25811.3157549165. The cubic root of 666224021 is about 873.3870786256.

Adding to 666224021 its reverse (120422666), we get a palindrome (786646687).

The spelling of 666224021 in words is "six hundred sixty-six million, two hundred twenty-four thousand, twenty-one".