691912909 has 2 divisors, whose sum is σ = 691912910. Its totient is φ = 691912908.

The previous prime is 691912877. The next prime is 691912927. The reversal of 691912909 is 909219196.

691912909 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 443944900 + 247968009 = 21070^2 + 15747^2 .

It is a cyclic number.

It is not a de Polignac number, because 691912909 - 2⁵ = 691912877 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (691912009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345956454 + 345956455.

It is an arithmetic number, because the mean of its divisors is an integer number (345956455).

Almost surely, 2^691912909 is an apocalyptic number.

It is an amenable number.

691912909 is a deficient number, since it is larger than the sum of its proper divisors (1).

691912909 is an equidigital number, since it uses as much as digits as its factorization.

691912909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 78732, while the sum is 46.

The square root of 691912909 is about 26304.2374723161. The cubic root of 691912909 is about 884.4714343002.

The spelling of 691912909 in words is "six hundred ninety-one million, nine hundred twelve thousand, nine hundred nine".