66506681 has 6 divisors (see below), whose sum is σ = 68091210. Its totient is φ = 64958208.

The previous prime is 66506641. The next prime is 66506683. The reversal of 66506681 is 18660566.

It can be written as a sum of positive squares in only one way, i.e., 65351056 + 1155625 = 8084^2 + 1075^2 .

It is not a de Polignac number, because 66506681 - 2¹⁰ = 66505657 is a prime.

It is a super-2 number, since 2×66506681² = 8846277235271522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66506683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 16136 + ... + 19833.

It is an arithmetic number, because the mean of its divisors is an integer number (11348535).

Almost surely, 2^66506681 is an apocalyptic number.

It is an amenable number.

66506681 is a deficient number, since it is larger than the sum of its proper divisors (1584529).

66506681 is an equidigital number, since it uses as much as digits as its factorization.

66506681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36055 (or 36012 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 38.

The square root of 66506681 is about 8155.1628432546. The cubic root of 66506681 is about 405.1555181839.

It can be divided in two parts, 6650 and 6681, that added together give a palindrome (13331).

The spelling of 66506681 in words is "sixty-six million, five hundred six thousand, six hundred eighty-one".