66207681 has 6 divisors (see below), whose sum is σ = 95633330. Its totient is φ = 44138448.

The previous prime is 66207671. The next prime is 66207697. The reversal of 66207681 is 18670266.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 57153600 + 9054081 = 7560^2 + 3009^2 .

It is not a de Polignac number, because 66207681 - 2²⁵ = 32653249 is a prime.

It is a super-2 number, since 2×66207681² = 8766914046795522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66207601) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3678196 + ... + 3678213.

Almost surely, 2^66207681 is an apocalyptic number.

It is an amenable number.

66207681 is a deficient number, since it is larger than the sum of its proper divisors (29425649).

66207681 is a wasteful number, since it uses less digits than its factorization.

66207681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7356415 (or 7356412 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 66207681 is about 8136.8102472652. The cubic root of 66207681 is about 404.5474414458.

The spelling of 66207681 in words is "sixty-six million, two hundred seven thousand, six hundred eighty-one".