6505256781 has 12 divisors (see below), whose sum is σ = 9436813308. Its totient is φ = 4318223424.

The previous prime is 6505256767. The next prime is 6505256789. The reversal of 6505256781 is 1876525056.

6505256781 is a `hidden beast` number, since 6 + 5 + 0 + 5 + 2 + 567 + 81 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 1610015625 + 4895241156 = 40125^2 + 69966^2 .

It is not a de Polignac number, because 6505256781 - 2⁵ = 6505256749 is a prime.

It is a super-2 number, since 2×6505256781² = 84636731573492963922, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6505256789) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1548990 + ... + 1553183.

It is an arithmetic number, because the mean of its divisors is an integer number (786401109).

Almost surely, 2^6505256781 is an apocalyptic number.

It is an amenable number.

6505256781 is a deficient number, since it is larger than the sum of its proper divisors (2931556527).

6505256781 is a wasteful number, since it uses less digits than its factorization.

6505256781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3102412 (or 3102409 counting only the distinct ones).

The product of its (nonzero) digits is 504000, while the sum is 45.

The square root of 6505256781 is about 80655.1720660244. The cubic root of 6505256781 is about 1866.7585452473.

The spelling of 6505256781 in words is "six billion, five hundred five million, two hundred fifty-six thousand, seven hundred eighty-one".