66029681561 has 2 divisors, whose sum is σ = 66029681562. Its totient is φ = 66029681560.

The previous prime is 66029681539. The next prime is 66029681563. The reversal of 66029681561 is 16518692066.

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., 63633089536 + 2396592025 = 252256^2 + 48955^2 .

It is a cyclic number.

It is not a de Polignac number, because 66029681561 - 2³⁴ = 48849812377 is a prime.

It is a Sophie Germain prime.

Together with 66029681563, 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 (66029681563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33014840780 + 33014840781.

It is an arithmetic number, because the mean of its divisors is an integer number (33014840781).

Almost surely, 2^66029681561 is an apocalyptic number.

It is an amenable number.

66029681561 is a deficient number, since it is larger than the sum of its proper divisors (1).

66029681561 is an equidigital number, since it uses as much as digits as its factorization.

66029681561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 933120, while the sum is 50.

The spelling of 66029681561 in words is "sixty-six billion, twenty-nine million, six hundred eighty-one thousand, five hundred sixty-one".