691309 has 2 divisors, whose sum is σ = 691310. Its totient is φ = 691308.

The previous prime is 691297. The next prime is 691333. The reversal of 691309 is 903196.

It is a happy number.

691309 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., 675684 + 15625 = 822^2 + 125^2 .

It is a cyclic number.

It is not a de Polignac number, because 691309 - 2⁷ = 691181 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (691349) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345654 + 345655.

It is an arithmetic number, because the mean of its divisors is an integer number (345655).

2⁶⁹¹³⁰⁹ is an apocalyptic number.

It is an amenable number.

691309 is a deficient number, since it is larger than the sum of its proper divisors (1).

691309 is an equidigital number, since it uses as much as digits as its factorization.

691309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1458, while the sum is 28.

The square root of 691309 is about 831.4499383607. The cubic root of 691309 is about 88.4214034017.

It can be divided in two parts, 69130 and 9, that multiplied together give a triangular number (622170 = T₁₁₁₅).

The spelling of 691309 in words is "six hundred ninety-one thousand, three hundred nine".