691729 has 2 divisors, whose sum is σ = 691730. Its totient is φ = 691728.

The previous prime is 691727. The next prime is 691739. The reversal of 691729 is 927196.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 677329 + 14400 = 823^2 + 120^2 .

It is a cyclic number.

It is not a de Polignac number, because 691729 - 2¹ = 691727 is a prime.

Together with 691727, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 691694 and 691703.

It is not a weakly prime, because it can be changed into another prime (691721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345864 + 345865.

It is an arithmetic number, because the mean of its divisors is an integer number (345865).

2⁶⁹¹⁷²⁹ is an apocalyptic number.

It is an amenable number.

691729 is a deficient number, since it is larger than the sum of its proper divisors (1).

691729 is an equidigital number, since it uses as much as digits as its factorization.

691729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6804, while the sum is 34.

The square root of 691729 is about 831.7024708392. The cubic root of 691729 is about 88.4393063805.

The spelling of 691729 in words is "six hundred ninety-one thousand, seven hundred twenty-nine".