691855 has 4 divisors (see below), whose sum is σ = 830232. Its totient is φ = 553480.

The previous prime is 691843. The next prime is 691871. The reversal of 691855 is 558196.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 691855 - 2⁷ = 691727 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 691855.

It is a congruent number.

It is an unprimeable number.

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, 69181 + ... + 69190.

It is an arithmetic number, because the mean of its divisors is an integer number (207558).

2⁶⁹¹⁸⁵⁵ is an apocalyptic number.

691855 is a deficient number, since it is larger than the sum of its proper divisors (138377).

691855 is a wasteful number, since it uses less digits than its factorization.

691855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138376.

The product of its digits is 10800, while the sum is 34.

The square root of 691855 is about 831.7782156320. The cubic root of 691855 is about 88.4446758610. Note that the first 3 decimals are identical.

The spelling of 691855 in words is "six hundred ninety-one thousand, eight hundred fifty-five".