691761641 has 2 divisors, whose sum is σ = 691761642. Its totient is φ = 691761640.

The previous prime is 691761617. The next prime is 691761643. The reversal of 691761641 is 146167196.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 579846400 + 111915241 = 24080^2 + 10579^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691761641 is a prime.

It is a Sophie Germain prime.

Together with 691761643, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (691761643) 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, 345880820 + 345880821.

It is an arithmetic number, because the mean of its divisors is an integer number (345880821).

Almost surely, 2^691761641 is an apocalyptic number.

It is an amenable number.

691761641 is a deficient number, since it is larger than the sum of its proper divisors (1).

691761641 is an equidigital number, since it uses as much as digits as its factorization.

691761641 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54432, while the sum is 41.

The square root of 691761641 is about 26301.3619609327. The cubic root of 691761641 is about 884.4069743687.

The spelling of 691761641 in words is "six hundred ninety-one million, seven hundred sixty-one thousand, six hundred forty-one".