8640064781 has 2 divisors, whose sum is σ = 8640064782. Its totient is φ = 8640064780.

The previous prime is 8640064757. The next prime is 8640064813. The reversal of 8640064781 is 1874600468.

8640064781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 8440096900 + 199967881 = 91870^2 + 14141^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8640064781 is a prime.

It is a super-2 number, since 2×8640064781² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8640064681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4320032390 + 4320032391.

It is an arithmetic number, because the mean of its divisors is an integer number (4320032391).

Almost surely, 2^8640064781 is an apocalyptic number.

It is an amenable number.

8640064781 is a deficient number, since it is larger than the sum of its proper divisors (1).

8640064781 is an equidigital number, since it uses as much as digits as its factorization.

8640064781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 258048, while the sum is 44.

The square root of 8640064781 is about 92951.9487746223. The cubic root of 8640064781 is about 2051.9762644229.

The spelling of 8640064781 in words is "eight billion, six hundred forty million, sixty-four thousand, seven hundred eighty-one".