691409 has 2 divisors, whose sum is σ = 691410. Its totient is φ = 691408.

The previous prime is 691399. The next prime is 691433. The reversal of 691409 is 904196.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 394384 + 297025 = 628^2 + 545^2 .

It is a cyclic number.

It is not a de Polignac number, because 691409 - 2⁸ = 691153 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (691489) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345704 + 345705.

It is an arithmetic number, because the mean of its divisors is an integer number (345705).

2⁶⁹¹⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

691409 is a deficient number, since it is larger than the sum of its proper divisors (1).

691409 is an equidigital number, since it uses as much as digits as its factorization.

691409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 691409 is about 831.5100720977. The cubic root of 691409 is about 88.4256666733.

The spelling of 691409 in words is "six hundred ninety-one thousand, four hundred nine".