66647281 has 2 divisors, whose sum is σ = 66647282. Its totient is φ = 66647280.

The previous prime is 66647279. The next prime is 66647309. The reversal of 66647281 is 18274666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 53802225 + 12845056 = 7335^2 + 3584^2 .

It is a cyclic number.

It is not a de Polignac number, because 66647281 - 2¹ = 66647279 is a prime.

It is a super-2 number, since 2×66647281² = 8883720129385922, which contains 22 as substring.

Together with 66647279, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (66647201) 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, 33323640 + 33323641.

It is an arithmetic number, because the mean of its divisors is an integer number (33323641).

Almost surely, 2^66647281 is an apocalyptic number.

It is an amenable number.

66647281 is a deficient number, since it is larger than the sum of its proper divisors (1).

66647281 is an equidigital number, since it uses as much as digits as its factorization.

66647281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 96768, while the sum is 40.

The square root of 66647281 is about 8163.7785981738. The cubic root of 66647281 is about 405.4408267146.

The spelling of 66647281 in words is "sixty-six million, six hundred forty-seven thousand, two hundred eighty-one".