681940685209 has 45 divisors (see below), whose sum is σ = 840572584917. Its totient is φ = 553132043352.

The previous prime is 681940685197. The next prime is 681940685213. The reversal of 681940685209 is 902586049186.

The square root of 681940685209 is 825797.

It is a perfect power (a square), and thus also a powerful number.

681940685209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 681940685209 - 2⁵ = 681940685177 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (681940685009) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 768816564 + ... + 768817450.

Almost surely, 2^681940685209 is an apocalyptic number.

681940685209 is the 825797-th square number.

681940685209 is the 412899-th centered octagonal number.

It is an amenable number.

681940685209 is a deficient number, since it is larger than the sum of its proper divisors (158631899708).

681940685209 is an frugal number, since it uses more digits than its factorization.

681940685209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1840 (or 913 counting only the distinct ones).

The product of its (nonzero) digits is 7464960, while the sum is 58.

The spelling of 681940685209 in words is "six hundred eighty-one billion, nine hundred forty million, six hundred eighty-five thousand, two hundred nine".