66583720217 has 24 divisors (see below), whose sum is σ = 79132861512. Its totient is φ = 55844812800.

The previous prime is 66583720207. The next prime is 66583720243. The reversal of 66583720217 is 71202738566.

It can be written as a sum of positive squares in 4 ways, for example, as 359329936 + 66224390281 = 18956^2 + 257341^2 .

It is not a de Polignac number, because 66583720217 - 2⁶ = 66583720153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66583720207) 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 in 23 ways as a sum of consecutive naturals, for example, 519167 + ... + 634587.

It is an arithmetic number, because the mean of its divisors is an integer number (3297202563).

Almost surely, 2^66583720217 is an apocalyptic number.

It is an amenable number.

66583720217 is a deficient number, since it is larger than the sum of its proper divisors (12549141295).

66583720217 is a wasteful number, since it uses less digits than its factorization.

66583720217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115689 (or 115682 counting only the distinct ones).

The product of its (nonzero) digits is 846720, while the sum is 47.

The spelling of 66583720217 in words is "sixty-six billion, five hundred eighty-three million, seven hundred twenty thousand, two hundred seventeen".