6681581 has 2 divisors, whose sum is σ = 6681582. Its totient is φ = 6681580.

The previous prime is 6681557. The next prime is 6681589. The reversal of 6681581 is 1851866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3740356 + 2941225 = 1934^2 + 1715^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6681581 is a prime.

It is a super-2 number, since 2×6681581² = 89287049319122, which contains 22 as substring.

It is an Ulam number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6681589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3340790 + 3340791.

It is an arithmetic number, because the mean of its divisors is an integer number (3340791).

Almost surely, 2^6681581 is an apocalyptic number.

It is an amenable number.

6681581 is a deficient number, since it is larger than the sum of its proper divisors (1).

6681581 is an equidigital number, since it uses as much as digits as its factorization.

6681581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11520, while the sum is 35.

The square root of 6681581 is about 2584.8754322017. The cubic root of 6681581 is about 188.3474504954.

The spelling of 6681581 in words is "six million, six hundred eighty-one thousand, five hundred eighty-one".