691689 has 4 divisors (see below), whose sum is σ = 922256. Its totient is φ = 461124.

The previous prime is 691687. The next prime is 691693. The reversal of 691689 is 986196.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 691689 - 2¹ = 691687 is a prime.

It is an Ulam number.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (691681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 115279 + ... + 115284.

It is an arithmetic number, because the mean of its divisors is an integer number (230564).

2⁶⁹¹⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

691689 is a deficient number, since it is larger than the sum of its proper divisors (230567).

691689 is a wasteful number, since it uses less digits than its factorization.

691689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 230566.

The product of its digits is 23328, while the sum is 39.

The square root of 691689 is about 831.6784234306. The cubic root of 691689 is about 88.4376016472.

The spelling of 691689 in words is "six hundred ninety-one thousand, six hundred eighty-nine".