66678687661 has 2 divisors, whose sum is σ = 66678687662. Its totient is φ = 66678687660.

The previous prime is 66678687637. The next prime is 66678687749. The reversal of 66678687661 is 16678687666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64043918761 + 2634768900 = 253069^2 + 51330^2 .

It is a cyclic number.

It is not a de Polignac number, because 66678687661 - 2⁵ = 66678687629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66678687961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33339343830 + 33339343831.

It is an arithmetic number, because the mean of its divisors is an integer number (33339343831).

Almost surely, 2^66678687661 is an apocalyptic number.

It is an amenable number.

66678687661 is a deficient number, since it is larger than the sum of its proper divisors (1).

66678687661 is an equidigital number, since it uses as much as digits as its factorization.

66678687661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 146313216, while the sum is 67.

The spelling of 66678687661 in words is "sixty-six billion, six hundred seventy-eight million, six hundred eighty-seven thousand, six hundred sixty-one".