66681 has 12 divisors (see below), whose sum is σ = 99840. Its totient is φ = 42840.

The previous prime is 66653. The next prime is 66683. The reversal of 66681 is 18666.

It is not a de Polignac number, because 66681 - 2⁶ = 66617 is a prime.

It is a super-2 number, since 2×66681² = 8892711522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (66683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 160 + ... + 398.

It is an arithmetic number, because the mean of its divisors is an integer number (8320).

2⁶⁶⁶⁸¹ is an apocalyptic number.

It is an amenable number.

66681 is a deficient number, since it is larger than the sum of its proper divisors (33159).

66681 is a wasteful number, since it uses less digits than its factorization.

66681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 276 (or 273 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 66681 is about 258.2266446361. The cubic root of 66681 is about 40.5509190365.

It can be divided in two parts, 666 and 81, that added together give a palindrome (747).

The spelling of 66681 in words is "sixty-six thousand, six hundred eighty-one".