66665321 has 2 divisors, whose sum is σ = 66665322. Its totient is φ = 66665320.

The previous prime is 66665311. The next prime is 66665323. The reversal of 66665321 is 12356666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64577296 + 2088025 = 8036^2 + 1445^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66665321 is a prime.

Together with 66665323, it forms a pair of twin primes.

It is a Chen prime.

It is a nialpdrome in base 10.

It is not a weakly prime, because it can be changed into another prime (66665323) 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, 33332660 + 33332661.

It is an arithmetic number, because the mean of its divisors is an integer number (33332661).

Almost surely, 2^66665321 is an apocalyptic number.

It is an amenable number.

66665321 is a deficient number, since it is larger than the sum of its proper divisors (1).

66665321 is an equidigital number, since it uses as much as digits as its factorization.

66665321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 38880, while the sum is 35.

The square root of 66665321 is about 8164.8834039440. The cubic root of 66665321 is about 405.4774048144.

The spelling of 66665321 in words is "sixty-six million, six hundred sixty-five thousand, three hundred twenty-one".