691280 has 20 divisors (see below), whose sum is σ = 1607412. Its totient is φ = 276480.

The previous prime is 691267. The next prime is 691289. The reversal of 691280 is 82196.

It can be written as a sum of positive squares in 2 ways, for example, as 107584 + 583696 = 328^2 + 764^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a hoax number, since the sum of its digits (26) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691289) by changing a digit.

691280 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4241 + ... + 4400.

2⁶⁹¹²⁸⁰ is an apocalyptic number.

It is an amenable number.

691280 is an abundant number, since it is smaller than the sum of its proper divisors (916132).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

691280 is a wasteful number, since it uses less digits than its factorization.

691280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8654 (or 8648 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 691280 is about 831.4324987634. The cubic root of 691280 is about 88.4201669761.

The spelling of 691280 in words is "six hundred ninety-one thousand, two hundred eighty".