681507581 has 2 divisors, whose sum is σ = 681507582. Its totient is φ = 681507580.

The previous prime is 681507571. The next prime is 681507601. The reversal of 681507581 is 185705186.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 341695225 + 339812356 = 18485^2 + 18434^2 .

It is a cyclic number.

It is not a de Polignac number, because 681507581 - 2⁶ = 681507517 is a prime.

It is a super-2 number, since 2×681507581² = 928905165920943122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (681507521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340753790 + 340753791.

It is an arithmetic number, because the mean of its divisors is an integer number (340753791).

Almost surely, 2^681507581 is an apocalyptic number.

It is an amenable number.

681507581 is a deficient number, since it is larger than the sum of its proper divisors (1).

681507581 is an equidigital number, since it uses as much as digits as its factorization.

681507581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 67200, while the sum is 41.

The square root of 681507581 is about 26105.7001629912. The cubic root of 681507581 is about 880.0153152465.

The spelling of 681507581 in words is "six hundred eighty-one million, five hundred seven thousand, five hundred eighty-one".