681082561 has 2 divisors, whose sum is σ = 681082562. Its totient is φ = 681082560.

The previous prime is 681082559. The next prime is 681082573. The reversal of 681082561 is 165280186.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 476592561 + 204490000 = 21831^2 + 14300^2 .

It is a cyclic number.

It is not a de Polignac number, because 681082561 - 2¹ = 681082559 is a prime.

Together with 681082559, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 681082561.

It is not a weakly prime, because it can be changed into another prime (681082511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340541280 + 340541281.

It is an arithmetic number, because the mean of its divisors is an integer number (340541281).

Almost surely, 2^681082561 is an apocalyptic number.

It is an amenable number.

681082561 is a deficient number, since it is larger than the sum of its proper divisors (1).

681082561 is an equidigital number, since it uses as much as digits as its factorization.

681082561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23040, while the sum is 37.

The square root of 681082561 is about 26097.5585256552. The cubic root of 681082561 is about 879.8323376345.

The spelling of 681082561 in words is "six hundred eighty-one million, eighty-two thousand, five hundred sixty-one".