8640039781 has 2 divisors, whose sum is σ = 8640039782. Its totient is φ = 8640039780.

The previous prime is 8640039773. The next prime is 8640039797. The reversal of 8640039781 is 1879300468.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 8293744900 + 346294881 = 91070^2 + 18609^2 .

It is a cyclic number.

It is not a de Polignac number, because 8640039781 - 2³ = 8640039773 is a prime.

It is a super-2 number, since 2×8640039781² (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 (8640039731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4320019890 + 4320019891.

It is an arithmetic number, because the mean of its divisors is an integer number (4320019891).

Almost surely, 2^8640039781 is an apocalyptic number.

It is an amenable number.

8640039781 is a deficient number, since it is larger than the sum of its proper divisors (1).

8640039781 is an equidigital number, since it uses as much as digits as its factorization.

8640039781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 290304, while the sum is 46.

The square root of 8640039781 is about 92951.8142964407. The cubic root of 8640039781 is about 2051.9742852921.

The spelling of 8640039781 in words is "eight billion, six hundred forty million, thirty-nine thousand, seven hundred eighty-one".