66621206717 has 4 divisors (see below), whose sum is σ = 71745914940. Its totient is φ = 61496498496.

The previous prime is 66621206711. The next prime is 66621206731. The reversal of 66621206717 is 71760212666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 71760212666 = 2 ⋅35880106333.

It can be written as a sum of positive squares in 2 ways, for example, as 9445701721 + 57175504996 = 97189^2 + 239114^2 .

It is a cyclic number.

It is not a de Polignac number, because 66621206717 - 2²⁶ = 66554097853 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66621206711) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2562354092 + ... + 2562354117.

It is an arithmetic number, because the mean of its divisors is an integer number (17936478735).

Almost surely, 2^66621206717 is an apocalyptic number.

It is an amenable number.

66621206717 is a deficient number, since it is larger than the sum of its proper divisors (5124708223).

66621206717 is a wasteful number, since it uses less digits than its factorization.

66621206717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5124708222.

The product of its (nonzero) digits is 254016, while the sum is 44.

The spelling of 66621206717 in words is "sixty-six billion, six hundred twenty-one million, two hundred six thousand, seven hundred seventeen".