681209 has 4 divisors (see below), whose sum is σ = 694116. Its totient is φ = 668304.

The previous prime is 681179. The next prime is 681221. The reversal of 681209 is 902186.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 902186 = 2 ⋅451093.

It can be written as a sum of positive squares in 2 ways, for example, as 327184 + 354025 = 572^2 + 595^2 .

It is a cyclic number.

It is not a de Polignac number, because 681209 - 2¹² = 677113 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 681209.

It is not an unprimeable number, because it can be changed into a prime (681229) 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, 6374 + ... + 6479.

It is an arithmetic number, because the mean of its divisors is an integer number (173529).

2⁶⁸¹²⁰⁹ is an apocalyptic number.

It is an amenable number.

681209 is a deficient number, since it is larger than the sum of its proper divisors (12907).

681209 is a wasteful number, since it uses less digits than its factorization.

681209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12906.

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

The square root of 681209 is about 825.3538635034. The cubic root of 681209 is about 87.9886779511.

The spelling of 681209 in words is "six hundred eighty-one thousand, two hundred nine".