66451716209 has 2 divisors, whose sum is σ = 66451716210. Its totient is φ = 66451716208.

The previous prime is 66451716161. The next prime is 66451716263. The reversal of 66451716209 is 90261715466.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 48211863184 + 18239853025 = 219572^2 + 135055^2 .

It is a cyclic number.

It is not a de Polignac number, because 66451716209 - 2¹² = 66451712113 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (66451716299) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33225858104 + 33225858105.

It is an arithmetic number, because the mean of its divisors is an integer number (33225858105).

Almost surely, 2^66451716209 is an apocalyptic number.

It is an amenable number.

66451716209 is a deficient number, since it is larger than the sum of its proper divisors (1).

66451716209 is an equidigital number, since it uses as much as digits as its factorization.

66451716209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 544320, while the sum is 47.

The spelling of 66451716209 in words is "sixty-six billion, four hundred fifty-one million, seven hundred sixteen thousand, two hundred nine".