691981061 has 2 divisors, whose sum is σ = 691981062. Its totient is φ = 691981060.

The previous prime is 691981057. The next prime is 691981099. The reversal of 691981061 is 160189196.

It is a happy number.

691981061 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 675220225 + 16760836 = 25985^2 + 4094^2 .

It is a cyclic number.

It is not a de Polignac number, because 691981061 - 2² = 691981057 is a prime.

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 (691981001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345990530 + 345990531.

It is an arithmetic number, because the mean of its divisors is an integer number (345990531).

Almost surely, 2^691981061 is an apocalyptic number.

It is an amenable number.

691981061 is a deficient number, since it is larger than the sum of its proper divisors (1).

691981061 is an equidigital number, since it uses as much as digits as its factorization.

691981061 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 41.

The square root of 691981061 is about 26305.5328970922. The cubic root of 691981061 is about 884.5004728865.

The spelling of 691981061 in words is "six hundred ninety-one million, nine hundred eighty-one thousand, sixty-one".