66778065605 has 4 divisors (see below), whose sum is σ = 80133678732. Its totient is φ = 53422452480.

The previous prime is 66778065577. The next prime is 66778065623. The reversal of 66778065605 is 50656087766.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 33150941476 + 33627124129 = 182074^2 + 183377^2 .

It is not a de Polignac number, because 66778065605 - 2²⁰ = 66777017029 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 in 3 ways as a sum of consecutive naturals, for example, 6677806556 + ... + 6677806565.

It is an arithmetic number, because the mean of its divisors is an integer number (20033419683).

Almost surely, 2^66778065605 is an apocalyptic number.

It is an amenable number.

66778065605 is a deficient number, since it is larger than the sum of its proper divisors (13355613127).

66778065605 is a wasteful number, since it uses less digits than its factorization.

66778065605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13355613126.

The product of its (nonzero) digits is 12700800, while the sum is 56.

The spelling of 66778065605 in words is "sixty-six billion, seven hundred seventy-eight million, sixty-five thousand, six hundred five".