681511813 has 4 divisors (see below), whose sum is σ = 681789868. Its totient is φ = 681233760.

The previous prime is 681511811. The next prime is 681511819. The reversal of 681511813 is 318115186.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 227949604 + 453562209 = 15098^2 + 21297^2 .

It is a cyclic number.

It is not a de Polignac number, because 681511813 - 2¹ = 681511811 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681511811) 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, 135318 + ... + 140263.

It is an arithmetic number, because the mean of its divisors is an integer number (170447467).

Almost surely, 2^681511813 is an apocalyptic number.

It is an amenable number.

681511813 is a deficient number, since it is larger than the sum of its proper divisors (278055).

681511813 is a wasteful number, since it uses less digits than its factorization.

681511813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 278054.

The product of its digits is 5760, while the sum is 34.

The square root of 681511813 is about 26105.7812179601. The cubic root of 681511813 is about 880.0171368047.

Adding to 681511813 its reverse (318115186), we get a palindrome (999626999).

The spelling of 681511813 in words is "six hundred eighty-one million, five hundred eleven thousand, eight hundred thirteen".