691720 has 16 divisors (see below), whose sum is σ = 1556460. Its totient is φ = 276672.

The previous prime is 691709. The next prime is 691721. The reversal of 691720 is 27196.

It can be written as a sum of positive squares in 2 ways, for example, as 605284 + 86436 = 778^2 + 294^2 .

It is not an unprimeable number, because it can be changed into a prime (691721) by changing a digit.

691720 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, 8607 + ... + 8686.

2⁶⁹¹⁷²⁰ is an apocalyptic number.

It is an amenable number.

691720 is an abundant number, since it is smaller than the sum of its proper divisors (864740).

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

691720 is a wasteful number, since it uses less digits than its factorization.

691720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17304 (or 17300 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 691720 is about 831.6970602329. The cubic root of 691720 is about 88.4389228213.

The spelling of 691720 in words is "six hundred ninety-one thousand, seven hundred twenty".