66206681 has 4 divisors (see below), whose sum is σ = 68489700. Its totient is φ = 63923664.

The previous prime is 66206663. The next prime is 66206689. The reversal of 66206681 is 18660266.

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 27206656 + 39000025 = 5216^2 + 6245^2 .

It is a cyclic number.

It is not a de Polignac number, because 66206681 - 2⁶ = 66206617 is a prime.

It is a super-2 number, since 2×66206681² = 8766649218071522, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66206689) 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 3 ways as a sum of consecutive naturals, for example, 1141466 + ... + 1141523.

It is an arithmetic number, because the mean of its divisors is an integer number (17122425).

Almost surely, 2^66206681 is an apocalyptic number.

It is an amenable number.

66206681 is a deficient number, since it is larger than the sum of its proper divisors (2283019).

66206681 is a wasteful number, since it uses less digits than its factorization.

66206681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2283018.

The product of its (nonzero) digits is 20736, while the sum is 35.

The square root of 66206681 is about 8136.7487978922. The cubic root of 66206681 is about 404.5454046757.

The spelling of 66206681 in words is "sixty-six million, two hundred six thousand, six hundred eighty-one".