1680918661 has 2 divisors, whose sum is σ = 1680918662. Its totient is φ = 1680918660.

The previous prime is 1680918599. The next prime is 1680918667. The reversal of 1680918661 is 1668190861.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1349460225 + 331458436 = 36735^2 + 18206^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1680918661 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1680918667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 840459330 + 840459331.

It is an arithmetic number, because the mean of its divisors is an integer number (840459331).

Almost surely, 2^1680918661 is an apocalyptic number.

It is an amenable number.

1680918661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1680918661 is an equidigital number, since it uses as much as digits as its factorization.

1680918661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 124416, while the sum is 46.

The square root of 1680918661 is about 40999.0080489760. The cubic root of 1680918661 is about 1189.0010355641.

The spelling of 1680918661 in words is "one billion, six hundred eighty million, nine hundred eighteen thousand, six hundred sixty-one".