666356321 has 2 divisors, whose sum is σ = 666356322. Its totient is φ = 666356320.

The previous prime is 666356281. The next prime is 666356323. The reversal of 666356321 is 123653666.

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., 448380625 + 217975696 = 21175^2 + 14764^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-666356321 is a prime.

It is a Sophie Germain prime.

Together with 666356323, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (666356323) 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, 333178160 + 333178161.

It is an arithmetic number, because the mean of its divisors is an integer number (333178161).

Almost surely, 2^666356321 is an apocalyptic number.

It is an amenable number.

666356321 is a deficient number, since it is larger than the sum of its proper divisors (1).

666356321 is an equidigital number, since it uses as much as digits as its factorization.

666356321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 116640, while the sum is 38.

The square root of 666356321 is about 25813.8784571401. The cubic root of 666356321 is about 873.4448877404. Note that the first 3 decimals are identical.

The spelling of 666356321 in words is "six hundred sixty-six million, three hundred fifty-six thousand, three hundred twenty-one".