1680206581 has 2 divisors, whose sum is σ = 1680206582. Its totient is φ = 1680206580.

The previous prime is 1680206579. The next prime is 1680206587. The reversal of 1680206581 is 1856020861.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1440885681 + 239320900 = 37959^2 + 15470^2 .

It is a cyclic number.

It is not a de Polignac number, because 1680206581 - 2¹ = 1680206579 is a prime.

It is a super-2 number, since 2×1680206581² = 5646188309671419122, which contains 22 as substring.

Together with 1680206579, 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 1680206581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1680206587) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 840103290 + 840103291.

It is an arithmetic number, because the mean of its divisors is an integer number (840103291).

Almost surely, 2^1680206581 is an apocalyptic number.

It is an amenable number.

1680206581 is a deficient number, since it is larger than the sum of its proper divisors (1).

1680206581 is an equidigital number, since it uses as much as digits as its factorization.

1680206581 is an odious number, because the sum of its binary digits is odd.

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

The square root of 1680206581 is about 40990.3230165365. The cubic root of 1680206581 is about 1188.8331147992.

The spelling of 1680206581 in words is "one billion, six hundred eighty million, two hundred six thousand, five hundred eighty-one".