667681681 has 4 divisors (see below), whose sum is σ = 706957092. Its totient is φ = 628406272.

The previous prime is 667681667. The next prime is 667681691. The reversal of 667681681 is 186186766.

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 589518400 + 78163281 = 24280^2 + 8841^2 .

It is a cyclic number.

It is not a de Polignac number, because 667681681 - 2¹¹ = 667679633 is a prime.

It is a super-2 number, since 2×667681681² = 891597654285971522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (667681621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19637680 + ... + 19637713.

It is an arithmetic number, because the mean of its divisors is an integer number (176739273).

Almost surely, 2^667681681 is an apocalyptic number.

It is an amenable number.

667681681 is a deficient number, since it is larger than the sum of its proper divisors (39275411).

667681681 is a wasteful number, since it uses less digits than its factorization.

667681681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39275410.

The product of its digits is 580608, while the sum is 49.

The square root of 667681681 is about 25839.5371669076. The cubic root of 667681681 is about 874.0235882705.

The spelling of 667681681 in words is "six hundred sixty-seven million, six hundred eighty-one thousand, six hundred eighty-one".