691780 has 12 divisors (see below), whose sum is σ = 1452780. Its totient is φ = 276704.

The previous prime is 691763. The next prime is 691787. The reversal of 691780 is 87196.

It can be written as a sum of positive squares in 2 ways, for example, as 73984 + 617796 = 272^2 + 786^2 .

It is not an unprimeable number, because it can be changed into a prime (691787) by changing a digit.

691780 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17275 + ... + 17314.

It is an arithmetic number, because the mean of its divisors is an integer number (121065).

2⁶⁹¹⁷⁸⁰ is an apocalyptic number.

It is an amenable number.

691780 is an abundant number, since it is smaller than the sum of its proper divisors (761000).

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

691780 is a wasteful number, since it uses less digits than its factorization.

691780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34598 (or 34596 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 691780 is about 831.7331302768. The cubic root of 691780 is about 88.4414798202.

It can be divided in two parts, 69 and 1780, that added together give a square (1849 = 43²).

The spelling of 691780 in words is "six hundred ninety-one thousand, seven hundred eighty".