681985509 has 4 divisors (see below), whose sum is σ = 909314016. Its totient is φ = 454657004.

The previous prime is 681985477. The next prime is 681985511. The reversal of 681985509 is 905589186.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 681985509 - 2⁵ = 681985477 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681985529) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 113664249 + ... + 113664254.

It is an arithmetic number, because the mean of its divisors is an integer number (227328504).

Almost surely, 2^681985509 is an apocalyptic number.

It is an amenable number.

681985509 is a deficient number, since it is larger than the sum of its proper divisors (227328507).

681985509 is a wasteful number, since it uses less digits than its factorization.

681985509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 227328506.

The product of its (nonzero) digits is 777600, while the sum is 51.

The square root of 681985509 is about 26114.8522683932. The cubic root of 681985509 is about 880.2209797145.

The spelling of 681985509 in words is "six hundred eighty-one million, nine hundred eighty-five thousand, five hundred nine".