8109619781 has 4 divisors (see below), whose sum is σ = 8328798732. Its totient is φ = 7890440832.

The previous prime is 8109619759. The next prime is 8109619789. The reversal of 8109619781 is 1879169018.

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 4117275556 + 3992344225 = 64166^2 + 63185^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8109619781 is a prime.

It is a super-3 number, since 3×8109619781³ (a number of 31 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8109619789) 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, 109589420 + ... + 109589493.

It is an arithmetic number, because the mean of its divisors is an integer number (2082199683).

Almost surely, 2^8109619781 is an apocalyptic number.

It is an amenable number.

8109619781 is a deficient number, since it is larger than the sum of its proper divisors (219178951).

8109619781 is a wasteful number, since it uses less digits than its factorization.

8109619781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 219178950.

The product of its (nonzero) digits is 217728, while the sum is 50.

The square root of 8109619781 is about 90053.4273695344. The cubic root of 8109619781 is about 2009.0935725545.

The spelling of 8109619781 in words is "eight billion, one hundred nine million, six hundred nineteen thousand, seven hundred eighty-one".